top of page




XPLORASUB – Underwater Studies Association

The GES (Grupo de Exploração Subaquática) was founded in 6th of July 2005 as a team of divers with a common interest in areas only accessible through advanced diving. Recognising the importance of a continuous evolution, the team was setup so that critical mass could be obtained for the development of projects, to access high performance equipment and to share information, knowledge and experience. 

GES, that since September 2009 changed its name to XploraSub – Grupo de Exploração Subaquática, developed or took part in numerous activities, including the ones oriented towards continuous training, thus allowing the team to improve and consolidate its operability.


At the beginning of 2017, in order to open itself to the community and to enhance the group capacities, XploraSub establishes itself as a non-profit association, adding to its designation “Underwater Studies Association". XploraSub keeps the pursuit of knowledge and its dissemination as the main purpose of its activity.


XploraSub history writes itself, mainly, through the projects that have been or are being developed and through the deliverables made available and that are listed bellow.




One of the first activities of XploraSub consisted in the development of a set of procedures to carry out Ice Diving, on altitude. Such dives took place at Lagoa Comprida, Serra da Estrela, Portugal in January 2006.

For this event, specific training was carried out on ice diving techniques, health and safety, and search and rescue. From this event an Operations Manual was produced, where all the data related with the expedition was recorded. This Manual was updated, at a later stage, with relevant information for the use of Close Circuit rebreathers in such conditions.

From this activity, an article was published in the n.10 of the Portuguese Magazine Planeta d’Água, in March 2006 and at a later stage, a Workshop, by Pedro Ivo Arriegas, took place at the ExpoSub exhibition in 2008, at Montijo, Portugal.


Link para Mergulho sob o Gelo

Link para Publicação Mergulho sob o Gelo

Mergulho no Gelo 2006 - Caderno de Operações rev 2008.pdf


In March 2006 we started the training of several members of the team in Cave Diving.This took place in Mexico, at the Yucatan peninsula. The training was then extended, in Portugal, at the Maciço Calcário Estremenho (around 100km north of Lisbon), including dry caving.


Training was intense, with multiple dives in different conditions, incluing theory taking place in the classroom and simulations in dry conditions.


This allowed the team to learn about, work on and practice, amongst others, different types of caves, buoyancy control and trim, different types of propulsion techniques, several equipment rigging, initiation to underwater topography and essential survival techniques in an overhead environment as responses to incidents as lost or broken line, entangled diver, or loss of light, which sometimes were taken cumulatively with, for instance, zero visibility.


Link para Actividade Formação em Espeleomergulho



In September 2006 deep diving training, with trimix gas mixtures (helium, nitrogen and oxygen), was carried out at Sharm El Sheik, Red Sea an activity which was continued in March 2007.  Series of deep dives were completed, with a maximum depth around 130m being achieved.

Mar Vermelho 2016

Mar Vermelho 2017


The project DAGO started in 2005 and was extended, in operational terms, until 2012.
In 15th of March 1942, the SS Dago, a British merchant vessel commissioned to the war effort, was sunk by a Focke-Wulf FW 200 Condor German bomber. This event took place 4 miles southwest of the Peniche coast, Portugal. The crew was helped by a motorized life-boat from Peniche. SS Dago rests today at a depth of 50m, only 500m away from another wreck.
Being off-shore and at depth it is not an easy dive, requiring good weather conditions and experience, training, equipment and adequate surface support.

In August 2007 all the necessary conditions had been fulfilled to start a research project around the SS Dago. The late GEPS – Grupo de Estudos e Pesquisas Subaquáticas was looking for a team of divers with the training, experience and interest to study this wreck. At the same time XploraSub was looking for scientific guidance with the same objective. From the collaboration between these two teams and with the collaboration of Armando Ribeiro, for photography, and Paulo Costa, author of the first national published article on the sinking and probably the first person that took an interest in the wreck from a historiographycal point of view and that had gathered important and vast documentation on the wreck, the project kicked off with workshops on steam technology and on methods of archeographic registration.
The project had two fundamental components running simultaneously: historiography and documentation, and the wreck site.
The dives continued with the purpose of identifying the wreck and after completing its mapping, confirmming that this wreck was indeed the SS Dago. The match could be checked via the measurements done, orientation and context of the wreck and most importantly, via the most noticeable dimensions of the structure that were compared with the SS Dago plans. This match can today be guaranteed.
The research allowed a full reconstruction of that WWII episode and confirmed that, the wreck commonly called “Dago” was indeed the SS Dago. However, the identity of the second wreck could not be determined.  

In terms of sponsorships, Peniche Municipality and the bank “Caixa de Crédito Agrícola” supported the project from 2007 to 2010 with, respectively, 2.000€ and 1.000€. Nevertheless these were scarse resources considering all the logistical costs incurred by the project (boat operators, gas mixes, food and lodging, equipment, travelling, etc.) which was on the field until 2012.

Several deliverables (articles, seminars, exhibitions and award) of this project deserve to be mentioned: 


In 2010 the leafleat “Peniche, Diving Paradise – SS Dago” was produced, with text by Paulo Costa and Jorge Russo, and photography by Armando Ribeiro. 


In January 2011, in the Lusotek 2011, 1st Portuguese conference on Technical Diving, Paulo Costa and Jorge Russo gave an update on the project with the presentation “SS Dago – research of a sinking”.

Several articles were also published on this subject:

Russo, J., 2011, SS Dago. Tech Diving Mag, 2, pages 35-41.

Russo, J., 2012, SS Dago, Wreck Portugal. Xray Magazine, 49, pages 12-16.  

Russo, J., 2012, SS Dago – De destroço a navio - Arqueografia Comparativa, Relatório à DGPC, Lisboa. 

Russo, J., 2012, História da investigação arqueológica em torno do SS Dago. National Geographic-Portugal.  

In 2012 Jorge Russo gave a presentation at Jornadas do Mar (Escola Naval) SS Dago: Historiografia de um destroço, which was Awarded Winning Work (1st Stage). 

In 2012 Annual Conference of the Nautical Archaeology Society (United Kingdom) a poster on SS Dago “From Wreck To Ship”, from Jorge Russo with photografies by Manuel Leotte and Armando Ribeiro, was presented. 


In 2013, at Centro Português de Actividades Subaquáticas (CPAS), at Lisbon, the lecture “SS Dago - Historiografia de um Destroço” was given by Jorge Russo and Paulo Costa, on the historiographycal research around SS Dago. This lecture was accompanied by an exhibition of a set of artefacts linked to the history of SS Dago and the shipping companies to which her belonged. 

In July 2013 SS Dago was included in the list of adopted wrecks, under the programme Adopt a Wreck of the Nautical Archaeology Society (United Kingdom).  


In November 2013, SS Dago Wreck won the 2013 Adopt a Wreck Award. A lecture on the SS Dago was given by Jorge Russo, at the Annual Conference of the Nautical Archaeology Society, at Portsmouth.  

On the official page of the Nautical Archeology Society, about the 2013 Adopt Wreck Award: "The 2013 award was presented to Jorge Russo, for his teams work on the Wreck of the SS Dago. The SS Dago was bombed off Portugal on the 15th March 1942 and now lies in 50m of water. "


Jury comments: “This is an excellent project at a difficult depth in open water. The team overcame the problems of identification by survey at such depth by research into obtainable features and dimensions. We especially like the idea of devising and using the special callipers to measure the engine cylinders. The production of a physical scale model of the wreck by the adoptee was an unusual bonus, indicating the amount of effort that the author has undertaken to make project successful. Level of outreach was also very good."  


An article was published: Russo, J. 2014, SS Dago. International Journal of Nautical Archaeology, Volume 43, Issue 1, pages 192-195. 

In March 2014 the important exhibition "Time Salvaged from the Sea" was opened to the public at the National Archaeological Museum, where the SS Dago represented the contemporary chronology.


The catalog of this exhibition, published by Imprensa Nacional Casa da Moeda, included an article on the project of the SS Dago. 

In 2017, a short movie "À descoberta de Dago, o destroço mais visitado em mergulho de profundidade", by Aurélio Faria, with Jorge Ramalho and João Lúcio, is presented by SIC Notícias.

The SS Dago project facebook can be accessed in



Link para Actividade Estudo do SS Dago


Ice Diving
Deep Dive
Cave Dive
SS Dago
Dive 150m


As part of a international team (5 divers, 3 surface support staff and 1 photographer) the XploraSub diver Manuel Leotte, as part of the continuous training he had been carrying out, performed in June 2007 a dive at a depth of 150m, Red Sea, between Shark Observatory and Anemone City.


Preparation had begun several months in advance, with the study of decompression programs, equipment riggings and adpatations, swimming pool and shallow depth dives, safety drills, and a slow increase on depth.

2 support divers were placed at 60m and 100m, these divers ascending with the 3 bottom divers. For this dive Manuel used 5 cylinders with 4 different mixes (TX8/65, TX15/45, TX31/15 and EANx72) which were selected to be used, respectively, from 150m to 78m, from 78m to 36m, from 36 to 12m and from there to the surface. These mixes were chosen considering partial pressure of Oxygen, Nitrogen Narcosis and Isobaric Counter difusion.

A full article on this dive was published on the Portuguese magazine “Planeta d’Água” n.4 (Julho-Agosto 2007).


Link para Publicação 150 metros


At the end of April 2007, Manuel Leotte joined a support team for diver Janina Preisner, who was attempting to film a section of the Jolanda wreck, 160 meters deep, in Ras Mohammed, at the southern tip of Sinai, in an area prone to strong currents. 


Manuel, who did his dive on Closed Circuit Rebreather, would be responsible for the photographic coverage of part of the descent and ascent, between 50m and the surface.

After an unsuccessful first attempt, where the filming had become too dark and fuzzy and the section of the wreck was not the desired one, a second attempt was immediately scheduled.

Then everything went smoothly. After a quick descent, a section of the ship's bow was found at 159.8 meters and images with a much better quality were obtained. In addition, the Women's World Record in Wreck Diving had been beaten, after the previous 144 meter Adina Ochert record.


An article about this dive was published in Planeta d'Água magazine 5 (September-October 2007) and a lecture was given by Manuel Leotte at ExpoSub (Montijo, 2008).


Link para Publicação Jolanda 160 Project



The Olha da Grota, in Portunhos, Cantanhede, is a permanent exsurgence whose exploration dates back to the 60’s, with further episodes in 1983 and 2005. In 2010 NEUA decided to resume the exploration of this cave where, at its invitation, XploraSub participated occasionally.


The characteristics of the gallery (a forced gallery with a small section, large amount of sediment, oftenly a strong flow and absence of natural features for lifeline attachment), where the diver is invariably subject to zero visibility, with a high probability of being trapped on or of damaging the line, advised to solo diving and a side-mount configuration.

Link para Actividade Olho da Grota


Algar das Morenas is located in Vila do Alandroal, in the southeast border of the Estremoz-Cano aquifer system and has a total depth of 76.5 meters.


Earlier results of the exploration of this cave were summarized on a short report including a rudimentary sketch from a French team which explored the cave in 1983, without reaching its bottom.

In order to study the pit in its entirety and in an exhaustive way, XploraSub and AESDA began exploratory and registration work in August 2008, and confirmed the existing geological studies in the planimetric orientation, fault slope and lithology, defined its speleogenesis, performed its topography and captured underwater images.

Being one of the water catchment sites of the Alandroal Council, Algar das Morenas shows in its upper section some metallic stairs and concrete platforms, nowadays in disuse. Since the deepest part of the pit is not equipped with any structures and as the 2008 water level was 19 meters below the 1983 level, it was necessary to devise technical solutions that would overcome the considerable difficulties in accessing water, in order to start the underwater exploration.

Changes in the water level throughout the project forced a continuous adaptation to the circumstances, which required significant logistics and the support of a large dry crew. Safety equipment was first installed, then a floating platform was built, and finally a progressively improved system of cables and weight reducers, which allowed the surface support to descend and hoist the divers. At the same time, it was necessary to adjust the operational procedures of the divers, both for their equipment and their arrival in water.


During the exploration it was observed a beautiful gallery with three chambers separated by very protruding crests hanging from the ceiling and smooth walls covered with clay, where any progression could easily result in low or zero visibility scenarios. The bottom (maximum of 45 meters deep) was covered by a layer of sediment, estimated at about 30 cm, which, if disturbed, could significantly reduce the visibility. The navigation is simple under normal visibility conditions, but the same does not apply when in zero visibility. Given these conditions and realizing the scarcity and fragility of the mooring points, it became obvious that one could not force the lifeline without affecting safety.

Underwater images (photography and video) were captured but, given the peculiar characteristics of this cave, its quality has limitations.  


The underwater exploration of the Algar das Morenas was thus marked by three factors: the great amount of sediment and how fast the water clouded for visibilities close to zero as soon as the divers enter the water, rendering unproductive longer dives or series of diving days; the fragility of the scarce mooring points of the lifeline preventing the usual installation of safety equipment and making it difficult to collect topometric data; and the difficulty of divers in accessing water, plus water level variations, which has led to complex associated logistics and the availability of sufficient human resources for the descent and ascend of divers and the significant amount of equipment. 

The activities have so far been carried out with the participation of 31 speleologists, of whom only 6 dived. During 23 days, 25 dives were performed.

Additional immersions will be required to remove the floating platform (submerged) and other equipment, and to verify the possibility of further exploration through a small hole detected at the bottom of the cave.


A lecture on "Underground and Underwater Explorations in Alandroal Pits" was given by Rui Luís in February 2012 at the Portuguese Center for Underwater Activities (CPAS) in Lisbon.

A detailed article was published in the magazine Trogle nº 6 (September 2014) - Underground and Underwater Explorations in Morenas Cave Shaft - Alandroal, by Luís, R.F. (AESDA); Mergulho, R.F. (AESDA); Arriegas, P.I. (XploraSub) & Regala, R.T. (AESDA).  

Algares do Alandroal

Explorações Subterrâneas e Subaquáticas no Algar das Morenas - Alandroal

Exploration of Morenas Shaft, at Alandroal, in May 2013. Nice footage of the deployment of divers and of the deployment of divers on this exquisite cave. Underwater video and editing by Armando Ribeiro. Footage at the surface by Fátima Carvalho and Frederico Tatá Regala.

Exploration of Morenas Cave Shaft, at Alandroal, in May 2013

Jolanda 160
Olho da Grota


The source of the Almonda River (or "Olho do Moinho da Fonte") is located at the foothills of the Serra de Aire, in the southeast, where rises the underground hydrological network of the most extensive national karstic system, Almonda Cave.


The exploration of this system has been carried out for about 80 years, but due to its complexity and size, with a development of more than 10 km, it is not yet finished. The explorations in the 1980’s by the speleologists Neves and Thomas with the help of several associations deserve to be highlighted, since they have significantly increased the knowledge of the system, including in submerged areas.


In this cave some archaeological sites (from the Lower Paleolithic to the Roman period) have also been discovered, which have been studied since 1987. In archeological terms, and according to archaeologist João Zilhão, this is a system of deposits with few parallels worldwide, with representation of all stages of prehistory. 

In 1993 the cave was classified as Archaeological Heritage (Property of Public Interest). 

In cave diving, in addition to the usual implications of diving with compressed gases, such as decompression management or gaseous poisoning, there is a need to consider low or lack of visibility, a high risk of disorientation, the existence of restrictions and the impossibility of direct access to the surface. An underwater cave is certainly a hostile environment, only suitable for certified divers.

In 2007 members of the associations XploraSub, NEUA and SAGA restarted more systematically the equipment of the submerged area of the cave and the underwater topography.

Exploração das galerias submersas da gruta do Almonda

When we penetrate into the system, after the very narrow entrance, we come across an underground labyrinth, where several levels of galleries, which in themselves have multiple variants, overlap. Beyond this there is an underground lake, A Cisterna, after which the galleries become more defined, with greater size and depth.

Between 2008 and 2010 members of XploraSub and NEUA carried out regular work, first in the labyrinth zone and then in other submerged areas. The cave is re-equipped with lifeline and navigation signals, the systematic marking of the galleries is initiated and the topographic information improved. Errors are corrected, some secondary galleries are mapped, and the drawing is enriched by the addition of details.


These works constitute the embryo of the Almonda Project, which begins in 2011, when it is decided to structure the exploitation of the underwater zone, based on a partnership between XploraSub and NEUA, but also with other people, either individuals or members from other associations.

During this year a diving campaign is organized with the support of Renova and the CPAS filling station (managed by Forte-Faria), which lays the ground for a regular exploration of underwater areas. The deepest area of the Northern Gallery is reached, 78 m deep, located at 350 m from the entrance. No unexplored areas significant for the development of the system are found, but several branches of main galleries supposedly not visited before are explored.

The television report "Underwater Expedition to the Grotto Almonda finished Monday" on the SIC channel, written by the journalist Carla Castelo, with an image of Hugo Neves, on the Almonda Campaign, was broadcast in June 2011.

Expedição à Gruta do Almonda 2011

The final report of the Almonda Project's 2011 Campaign and its annexes (emergency, management, media and support, operational issues, risk, safety, and post-campaign), including operations documents are available at: 


Projecto Almonda Relatório da Campanha de 2011 

After this campaign it will be needed to survey certain secondary deep areas, located at the end of the North Gallery, and it will be necessary to adopt equipment configurations with a smaller volume, able of overcoming restrictions in the West Gallery. It is also estimated that, in due course, the work will be extended to dry areas.


A lecture on the Almonda Project was given by Miguel Lopes and Pedro Ivo at the Portuguese Center for Underwater Activities (CPAS) in Lisbon (February 2012).

In 2012, a second campaign is carried out, with a longer duration, which substantially benefits from the experience obtained in the previous year, and again with the support of Renova and Jorge Forte-Faria. Being mainly oriented to obtain topographic data, there is a significant increase of mapped submerged galleries. 162m from the West Gallery are mapped, standing the work front at 372 m from the entrance.


The final report of the 2012 Almonda Project Campaign and its annexes (management, media, operational issues, and post-campaign), including operations documents, are available at : 

Projecto Almonda - Relatório da Campanha de 2012

In 2013 the Almonda Project starts being developed by a partnership between XploraSub and AESDA. This year 28 dives are carried out, with an average duration of more than two hours and an average depth of 41 m. A good advance in the topography of several galleries is achieved and others are pointed out for future verification. Navigational equipment is also improved to make it more resistant to water flow during the rainy season and to abrasion, thus raising the level of safety. In the North Gallery steel cable is installed down to -66m, which requires to repeat some parts of the topography.

The consolidated report of the Almonda Project's 2013 activities is available at 


Projecto Almonda - Actividades em 2013 

In 2014, despite early rains, 18 immersions are carried out, with an average duration of almost two and a half hours, with an average depth of 30m maximum. Work begins in the dry zone, which allows to check the underwater topography and advance to an overall understanding of the system. Several underground passages from the submerged area to the dry area are indicated by divers, and their connection to the dry topography is then achieved. The submerged entrance of the cave is also geographically referenced. The navigational equipment continues to be repaired and improved, with replacement of worn out lifeline and already illegible labels. 

With the link between dry and submerged topography, it was possible to confirm the real position of the submerged and dry areas of the cave and to establish comparisons with previous publications.

A lecture on the Almonda Project was given by Pedro Ivo on the occasion of the launch of the 6th issue of Trogle magazine, at the Carsoscópio, Olhos de Água do Alviela (September 2014).

The consolidated report of the Almonda Project's 2014 activities is available at : 
Projecto Almonda - Actividades em 2014

An article about the Almonda Project, written by Pedro Ivo, was published in Revista de Marinha (May 2015).  


In 2015, 22 dives are made, with an average duration of almost two hours and an average maximum depth around -38m.
Dry work is continued in order to check the underwater topography and to refer it to the outside, also advancing in the global understanding of the system.
The repair, revision and correction of the navigation equipment (line, mooring and labels) in several galleries are carried out. Topometry of Gallery A is checked, revised or executed and the topography in a 1/100 scale of an important section of this gallery is finished. Underwater images (photography) are captured.
In the dry exploration, the two siphons of the West Gallery are overcome and the dry exploration of these same galleries is continued.

In 2015 are registered: 

  • Dry: 

Development of 323m, with a difference of 27m (+19m to -7m).
62 stations, with 0% error (no loops). 


  • Underwater:

Development of 916m, with a difference of 78m (0 to -78m).

277 stations, with 4.52% error.

  • Both dry and underwater after revision:

Development of 1264m, with a difference of 97m (+19 to -78m).
348 stations, with 3.68% error. 

Distance between the entrance of the cave and the intersection for Gallery W: 209.29m.
Distance between the intersection for Gallery W and the end of Gallery A: 139.81m.
Distance between the intersection for Gallery W and the presenteend of exploration in Gallery W: 162.65m.
With the dry/underwater topographic connection a reduction of the error is obtained: 4.72% to 3.77%, subsequently reduced to 3.68%. The Gallery P with data from 2014 is also integrated in the topometry. 


At the 6th National Congress of Speleology (October 2015) a lecture on "Underwater Explorations in the Eye of the Moinho da Fonte - Gruta do Almonda" is presented by Rui Luís and Pedro Ivo, and included in the Book of Minutes and Summaries, edited by the Federation Portuguese Speleology.

Explorações Subaquáticas no Olho do Moinho da Fonte – Gruta do Almonda

The consolidated report of Almonda Project's 2015 activities is available at 

Projecto Almonda - Actividades em 2015

In 2016, 21 dives are performed, with an average duration of 135 minutes and an average maximum depth of more than -43m.
Several galleries are drawn over the topometry to scale 1/100. Lifeline is also repaired in galleries A (North) and W (West) until station W49, and filming is performed on several dives.

Further work will allow to progress with the topometry and topography in other galleries, to lay the steel cable between -66m (A68) and the -78m, end of Gallery A, to establish other connections with dry areas, and to continue the work in the dry area of the cave.

The consolidated report of the Almonda Project's 2016 activities is available at

Projecto Almonda - Relatório Consolidado 2016


A video by Pedro Santos. Diving to the deepest area of Gallery A (or North).

Project Almonda, Autumn 2016

In May 2018, the no. 7 of the Trogle magazine is published, including the topography resulting from last years work, in the article “Underwater Exploration at Olho do Moinho da Fonte – Almonda’s Cave – update”, by Rui Luís and Pedro Ivo Arriegas. 

Publication - Trogle 7 

At the launch of the magazine, Rui Luís gives a presentation on the project.


The consolidated report of the Almonda Project's 2017 activities is available at 

Consolidated Report -Almonda Project's 2017 activities 

In December 2018 Armando Ribeiro and Rui Luís were speakers in Eurotek 2018 – Advanced Diving Conference, with a talk on the exploration of underwater caves in Portugal, including Almonda.

Rare footage by Armando Ribeiro from Gallery W (or West).

Project Almonda, July 2018

During the summer of 2020, dives are performed to restore several sections of the guideline.



Since 2014 divers from XploraSub have attended campaigns of this project of CINAV (Center for Naval Research), at the invitation of its coordinators Augusto Salgado and Jorge Russo. This project studies the episode of the Great War that occurred on April 24, 1917, when the submarine U-35 of the German Imperial Navy, under the command of the "Aces of the Aces" Lothar von Arnauld de la Perière, sank 4 ships off Sagres and Lagos.

In November 2014 the wrecks of SS Torvore, a Norwegian steam freighter, located off the coast of Sagres, between 24 and 30 meters deep, and of SS Nordsøen, a Danish steam freighter, in the area designated Ponta dos Caminhos, near Sagres, about 18 meters deep, were dived and studied.

Already in October of 2015 a new campaign dedicated to the study of the wreck of the SS Vilhelm Kragg, a Norwegian freighter, located off Luz, Lagos, around 36m deep, was carried out.

Project U-35 Facebook

Projeto U-35 website

This project was awarded the Adopt Wreck Award of 2015 from the Nautical Archeology Society, an award received by project coordinators Augusto Salgado and Jorge Russo at the NAS Annual Conference in Portsmouth, UK.

On the official page of the Nautical Archeology Society about the 2015 Adopt Wreck Award, with which the U-35 Project was awarded, it can be read:

“Portuguese Navy Research Centre for their U-35 Project: April, 24th 1917, the Imperial German submarine U-35, commanded by the "Ace of aces" Lothar von Arnauld de la Perière, sank 4 ships off Sagres and Lagos, Algarve, South Portugal. This is a Great War episode not mentioned in the history books that brought the war to continental Portugal, away from the classic view of the Belgium trenches and African territories. Project U-35 is researching into the history of the episode, detecting the multicultural and multinational footprint, and, identifying the wrecks alleged to correspond to the ships sank by the U-35 that day.”


The lecture "The History and Underwater Archeology of World War I: The Case of the Operations of U-35 off the Coast of Algarve, Portugal", by Augusto Salgado and Jorge Russo, was published In the minutes of the Scientific Conference for the Occasion of the Centennial of the First World War (Bruges, Belgium, June 2014). 

In 2014, the article "Correlação Destroço-Navio num dos navios afundados pelo U-35 no Algarve em 1917 - Ensaio de uma metodologia", by Jorge Russo and Augusto Salgado, was published.


In 2015 the report "Projecto U-35 (CINAV). Relatório dos trabalhos de 2014" by Augusto Salgado et al. was made available.

In 2017, the episode of April 24, 1917, in which the submarine U-35 of the German Imperial Navy led to the sinking of four merchant ships, is remembered in Vila do Bispo. A century later the wreckage of these vessels is now protected under the UNESCO Convention on the Protection of the Underwater Cultural Heritage.

The Municipality of Vila do Bispo wins the "Municipality of the Year Award 2017", at a regional level, with the project "Evocation of U35 Operations in Sagres (1917-2017)". 


In the same year the monography "Actions of the U-35 in the Algarve - April 24, 1917" by António José Telo, Augusto Alves Salgado and Jorge Russo is published.


Also in 2017 is broadcast by SIC Notícias, integrated in the programme Aqui há História, the episode "What is left of the German submarine U-35?", by Aurélio Faria and Amélia Moura Ramos, with camera by Jorge Ramalho and João Lúcio.


The Alviela spring is a permanent karst spring, the largest in the country, fed by the Planalto de Santo António.


It is located east of Alcanena at the overlapping contact of the Estremenho Limestone Massif with the Tertiary Basin of Lower Tagus, at the extreme west of the triangle Alviela, Almonda and Polje de Minde.

In 2017, after the approval of the plan of work by the Natural Park of the Serras de Aire and Candeeiros, the cavediving activities for the study of the source of the Olhos de Água of Alviela began, in partnership with AESDA.

In May 2018, the no. 7 of the Trogle magazine is published, where a note refers the progress achieved in the exploration of this cave, during 2017, with the connection of East and West sectors, through a 50 meters length passage at a 134 m depth. 

At the launch of the magazine, Armando Ribeiro gave a presentation about the project, where he integrated a shoot of the descent to the maximum recorded depth.


Video - XploraSub Alviela 2017

Photo: Armando Ribeiro


In September 2018 in a new underwater gallery, found at about 1000 meters from the source, the known maximum depth is exceeded. Divers Armando Ribeiro and Rui Luís from XploraSub/AESDA team reach 150 meters.

The consolidated report of the Olhos de Água do Alviela Project's 2017 activities is made available at

Consolidated Report -Olhos de Água do Alviela Project's 2017 activities 

In December 2018 Armando Ribeiro and Rui Luís were speakers in Eurotek 2018 – Advanced Diving Conference, with a talk on the exploration of underwater caves in Portugal, including Alviela.

In May 2019 Armando Ribeiro and Pedro Ivo, on the celebrations of the 40 years of the Natural Park of the Serras de Aire and Candeeiros (PNSAC), in Rio Maior, gave a lecture titled "Cave of the Spring of Alviela (technical and technological challenges in the exploration of the most important Portuguese karst spring)” and a photo exhibition by Armando Ribeiro, on the Alviela Project, was held at PNSAC headquarters, Rio Maior.

In May 2019 two decompression habitats were deployed in the main underwater tunnel of the spring of river Alviela.


Also in May 2019 Armando Ribeiro gave a lecture called "Underwater Exploration of the Olhos de Água Spring", at the 3rd edition of the ObservaCarso event, in Alviela, organized by the Municipal Council of Alcanena.

In May 2019, the consolidated report of the activities of the Olhos de Água do Alviela Project undertaken during 2018 is made available.

Alviela Project - 2018 Consolidated Report

In July and September 2019, as the exploration under the Alviela Project is progressing, the diver Armando Ribeiro, from XploraSub, surpasses the depth of 170 meters and then the depth of 190 meters! What a remarkable achievement! And the cave continues to go deeper.


Foto: Rui Mergulho

In November 2019, in the 7th National Speleology Congress, Rui Luís, Armando Ribeiro and Pedro Ivo Arriegas presented the lecture “Alviela, Exploration to the Deep”. The communication “Underwater explorations in the water springs of the Alviela” is included in the minutes of the Congress.

Alviela - 7º Congresso de Espeleologia

At the beginning of December 2019, the commemorative publication of the 40th anniversary of the creation of the Serras de Aire e Candeeiros Natural Park is launched. It includes the article “Technical and technological challenges in the exploration of the Alviela spring” by Armando Ribeiro, Pedro Ivo Arriegas and Rui Luís.

Desafios técnicos e tecnológicos na exploração da nascente do Alviela

In December 2019, XploraSub requested authorization to the Institute for the Conservation of Nature and Forests (ICNF, IP) to carry on the work under the Alviela Project during the year 2020, with the topography of the cave system, the filming of the western part and the deep exploration of the northern area.

In December 2019, a special report by Aurélio Faria and Rafael Homem, titled “Mergulho no Alviela”, is presented in the Jornal da Noite on the SIC television.

SIC - Mergulho no Alviela - Reportagem Especial

During 2020, the decompression bells are replaced and new guideline is installed in areas where it has been broken.

In August it is produced the consolidated report of the activities of 2019 of the Project of Olhos de Água do Alviela.

Projecto Alviela - Relatório Consolidado 2019

In September, divers Armando Ribeiro and José Mário Ventura, from XploraSub, installed again guideline back to a depth of 190 meters. In this dive José Ventura suffers an accident, whose symptoms point to a decompression sickness accident of the inner ear. His dive lasts more than 9 hours. The capacity of the entire team (in the water and on land), the safety measures implemented (namely the decompression bells) and the owner's experience, make it possible to bring the diver to the surface and the success of the rescue. José is taken to the hyperbaric chamber. Joana De Capitani is of paramount importance in this process and in the speed with which it occurs. This traumatic event leads us to reflect on what can be improved in terms of safety, with reinforced measures, which are immediately implemented.

2020 - In October, during the exploration of the underwater galleries of the source of the Alviela river, the XploraSub diver Armando Ribeiro, supported by an underwater and surface team, goes even deeper, rigging about 80 meters of new gallery with guideline beyond the previous depth mark of 190 meters and reaching 205 meters, at a distance of 1,2 km from the surface.

2020 - Still in October, in the exploration of the underwater galleries of the source of the river Alviela, the XploraSub diver Armando Ribeiro, with proper underwater and surface support, exceeds the distance reached in the previous dive and touches 215 meters depth.

This dive is the subject of a special report by Aurélio Faria and João Ramalho, named “Alviela, Maximum Depth”, is presented in the Jornal da Noite on the SIC television.

SIC - Mergulho no Alviela - Reportagem Especial 2020

2020 - At the end of October, National Geographic Portugal publishes in its Facebook page the album: Record in the aquatic exploration of caves in Portugal.


The source of the Ribeira da Pena, known as the cave of the Pena by cavedivers and Poio by speleologists, belongs to the karst complex of the caves of Mira D'Aire. It is located in the municipality of Porto de Mós, in the polje of Minde.

The Moinhos Velhos cave (together with Pena cave and Contenda cave), is part of a large network of galleries with more than 11 km in length, constituting one of the most important underground systems of the Estremenho Limestone Massif. It is characterized by the existence of two collectors, with tributaries drawing a dendritic network and a set of galleries to the north and angled to the south. The fossil zone has a level difference of 100 meters and the thickness of the intermediate zone varies between 80 meters upstream and 60 meters downstream, circulating the water through syngeneic galleries, from the north to the south quadrant, towards the exsurgence of the Pena cave.


For the XploraSub this cave is a cavediving training center. Easy access and low difficulty, it has all the characteristics to start a safer cavediving training during the rainy season (temporary exsurgency).



Of a rare beauty, it is also the focus of practice and improvement of underwater photography techniques, so essential to register other projects in which XploraSub is involved.


On May 12th and 13th took place LusoTek’ 2018, the 3rd Portuguese Technical Diving Conference, held at the Cultural Center of Carnide, and organized by Casco Antíguo, PhotoGuerra, Aquanautas, XploraSub and the Parish Council of Carnide.

We can define technical diving as a specialization of scuba diving, using techniques, procedures and specialized equipment, to safely surpass the limits of depth and time of recreational diving. Technical diving can be a tool in scientific projects, cultural or environmental, such as archeology, caving, biology or physiology.

The objectives were the communication of initiatives, activities and projects involving technical divers, the exchange of experiences, methodologies, results and lessons learned by the technical diving community and the dissemination among recreational divers and the general public. The entrance was free and 72 participants were present, with a considerable number of recreational divers.

The event were filled by lectures and ended with a visit to the Center for Underwater and Hyperbaric Medicine, at the Lisbon Military Health Campus. The presentations were appealing and addressed areas as diverse as Safety, Techniques, Expedition, Archeology or Speleology. The speakers had diverse backgrounds, including two Spanish speakers. Two members of XploraSub presented communications. Manuel Leotte gave the lecture "An Epiphany in a Shipwreck", related to the recovery of victims in a shipwreck in Nigeria, off the coast of Escravos, while Armando Ribeiro gave lectures on several expeditions he made and also (with Pedro Lage) on his expedition to the Britannic, the twin ship of the Titanic. 

Several companies, centers and diving schools raffled out boat dives, fillings, pool time and equipment among participants.

During the event there was also a photographic exhibition by several underwater photographers (including Armando Ribeiro and Rui Luís, of XploraSub), an exhibition that will circulate for three months on public spaces in the Parish of Carnide.




AESDA - Associação de Estudos Subterrâneos e Defesa do Ambiente 

CINAV - Centro de Investigação Naval 

CPAS - Centro Português de Atividades Subaquáticas 

GEPS - Grupo de Estudos e Pesquisas Subaquáticas 

GES - Grupo de Exploração Subaquática 

NAS - Nautical Archaeology Society 

NEUA - Núcleo de Espeleologia da Universidade de Aveiro 

SAGA - Sociedade dos Amigos das Grutas e Algares 

Moinhos Velhos
bottom of page