Project name:Alviela spring exploration
Nascentes do Alviela  important spring in Portugal

Nascentes do Alviela important spring in Portugal

Mainland Portugal has three main karst areas: Serras d’Aire and Candeeiros, Sicó-Alvaiázere and Arrábida mountain ridge. Arrábida is a limestone mountain leaning against the sea, where springs of fresh water are unknown. The other two areas, Serras d’Aire and Candeeiros and Sicó-Alvaiázere, are located inland and present some notable permanent karstic springs.

At Serras d’Aire and Candeeiros there are two main springs: Alviela and Almonda. Both are embedded in Jurassic limestones.

215m depth - deepest cave dive in Portugal Cave description and speleogenesis:

215m depth - deepest cave dive in Portugal Cave description and speleogenesis:

The Alviela spring is a permanent karst spring located to the West of Alcanena, in the gentle contact of the Estremenho Limestone Massif on the Tertiary Basin of the Lower Tagus, on the center of Portugal.

It lies at the western extreme of a triangle formed by Alviela spring, Almonda spring, on the East, and Minde’s Polje, on the North, in a small limestone block separated by a Cretaceous outcrop preserved within the Monsanto syncline, on the southernmost part of the Serras d’Aire and Candeeiros Natural Park (PNSAC).

Although the spring is permanent, it can only be dived during the dry season, when is possible to swim through more than 1250 meters of underwater tunnels, with a drop of -215 meters. In the dry entrance access to the water is difficult and time-consuming due to the various drops of 3 meters to overcome and a small tunnel of 10 meters and 1.3 meters height. During the rainy season it is virtually impossible to penetrate the system due to the strong current and flow rate.

PNSAC authorization is required.

215m depth - deepest cave dive in Portugal Continous pushing the boundaries

Constant reaching of further and deeper sections of the cave led to habitat installation and continuous secarch for better equipment, able to withstand extreme deep cave environment.

First underwater exploration, with 150 meters of linear development to a depth of 35 meters. Since then the cave has been explored mainly by Portuguese, Belgian, Spanish and French divers
J. Michel and J.P. Thiery reached 300 meters of development and 50 meters of depth.
In 2004 a Franco-Portuguese team reached a depth of 125 meters, with 1370 meters surveyed. In 2007 and 2008 the same team reached a depth of 130 meters, extending the topography to 1510 meters
B. Moulin and M. Burgui joined two passages at a depth of 134 meters, but did not manage to find the continuation of the cave.  
2016 -Start of Xplorasub work in Alviela
This Project, by the partnership AESDA/XploraSub, started with the study of relevant information to the understanding of the cave, namely the reports of previous explorations and available publications, and with some dives, focused on making ourselves familiar with the cave and to the evaluate the associated logistics and procedures. Dives: 9 Max time: 180 minutes Max depth:50 meters
During this year the guideline was checked, and repaired where needed, up to 110 in depth. We started mapping with traditional methods. Several dives were made in deep areas of the system, progressively increasing the duration, distance and depth, until reaching 134 meters depth, the maximum underwater depth in a national cave, previously reached by the Franco-Portuguese team. A restriction was negotiated and about 50 meters of line were placed connecting two deep passages. Several underwater images were captured, in video and photography. Dives: 31 Max time: 275 minutes Max depth: 134 meters However, this deeper area presents a lot of silt, which makes it doubtful that most of the water that emerges at the spring passes through there.
In 2018 we searched for the source of the water, exploring some branches detected during the previous year. The guideline had again to be repaired until 134 meters depth. A raid was made into a virgin tunnel and there 150 meters of depth were reached, at the time, an unprecedented mark in an underwater cave in Portugal. Underwater video footage was captured and an interview was given to the RTP1 national television evening news. Dives: 22 Max time: 220 minutes Max depth: 150 meters
Taking into account the great depth at which exploration was taking place and the long duration of dives, activities at the beginning of the year were mainly dedicated to rigging equipment, preparing logistics and improving procedures that can offer a greater safety to divers. Two decompression bells were prepared and placed with positive buoyancy against the tunnel ceiling, on a suitable location, at a depth around 7 meters. Redundant diving life support equipment, namely sidemount rebreathers, were repeatedly tested. An electronic navigation console Seacraft ENC2 was tuned and placed on a Seacraft Ghost Diver Propulsion Vehicle (DPV), for recording depth, distance and azimuth, in order to obtain a survey line of the cave at greater depths. There was a considerable evolution on the support to the push divers. Then we felt that the minimum conditions for the progress of the exploration were in place. The 174 meters depth was exceeded, with the laying of more than 60 meters of line on a virgin passage, and later 190 meters were reached, with line being laid in more 70 meters of this same passage. Dives:28 Max time:372 minutes Max depth: 190 meters In 2019, the team mapped more than 1200 meters underwater, including 200 meters of new cave, between 130 and 190 meters depth. In December 2019, a special report “Mergulho no Alviela” was presented on SIC national television evening news.
2020 was an atypical year. Dives started late, due to a heavy and long rainy season, shrinking the window to explore, activities were stopped by general confinement in response to the pandemic situation and finally health problems by one of the push divers and a diving accident of another diver seemed to turn unreachable the goals we set out for 2020, explore new passages and exceed the 190 meters depth. Only the resilience of the multidisciplinary team of members of AESDA and XploraSub made it possible that in only four months more than sixty dives were carried out, culminating on October 18th with a 215 meters depth mark, increasing the development of the underwater passages of Alviela by about 150 meters. In October 2020 the event was subject to a special report “Alviela, Profundidade Máxima” on SIC national television evening news. Dives:61 Max time: 375 minutes (in fact we had a casualty diver who had to spent 547 minutes underwater!) Max depth: 215 meters
Further 280 meters of new passages were discovered and surveyed, and a new passage connects the East and West sectors of the cave. The various mapped passages are at maximum depths of 134, 153 and 215 meters in depth. An updated topography of this underwater cave was released, with more than 2100 meters mapped and with 222 meters of total height gap - of which 215 are underwater. These results were only possible thanks to effective teamwork, with the huge dedication of more than a dozen involved cave divers. Tireless work of numerous speleologists was also a great help - they supported push divers in various procedures, namely those involved in decompression, helping in raising the safety levels of the entire operation and working hard on the transportation, preparation and placement of a large volume of equipment on dryland and underwater. The support of Seacraft was also critical. Max dive time: 481 minutes Max depth: 215 meters.
Further exploration will continue, in order to explore deeper parts of the cave. The objective is to enhance the knowledge of the cave system as a whole.

215m depth - deepest cave dive in Portugal Alviela maps


215m depth - deepest cave dive in Portugal Video from a dive

A video from the record dive in 2020

215m depth - deepest cave dive in Portugal National TV program

A short docummentary, showcasing effort and development of the project.

215m depth - deepest cave dive in Portugal Critical equipment

  • about ENC

The need to have a tool that would allow us to collect topographic data in an automatic, fast and accurate way, at depths where any waste of time is critical, led us to choose ENC. ENC proved to be an easy to handle and very reliable instrument. The fact that the information collected can be easily transferred to a computer for further processing is also an invaluable advantage.

  • about GHOST

For our exploration we were looking for a scooter that would allow us to go further, deeper and on which we could depend. When doing a market study, we found that the Ghost Seacraft could provide us with the features we needed, not only for the quality of the materials and the technology used, but also based on the reports of its use in some extreme explorations. In fact, the Ghost is a stunning machine, very well balanced, with fantastic performances, both in terms of range and speed, very easy to maneuver and to carry to the dive site. In short, when you want the best, it’s hard not to want one.

215m depth - deepest cave dive in Portugal Project photos


215m depth - deepest cave dive in Portugal About us

  • Curriculum Rui Luís

Born in 1978, speleologist since 1992 and diver since 2001.In 1992 he joined the team of cavers from AESDA – Association of Underground Studies and Environmental Defense, where he is responsible for the edition of the magazine Trogle and is currently chairman of the board.In Portugal it is known for having discovered, participated and explored the Algar do Bom Santo (most important Neolithic Necropolis), the Roman Mines of Valongo (largest roman mining complex), Algar Palopes (deeper cave in Portugal) among other projects related to archeology, paleontology and biospeleology.He is a trainer in the technical area of caving and underground photographer.

He has published several articles and participated in national and international congresses of the specialty.

In 2001 he started his dive training, currently being CCR Advanced Mixed Gas Diver, Full Cave Diver, photography and underwater archeology.

He is currently responsible for the cave diving department of Xplorasub – Association of Underwater Studies and co-responsible for the exploration of several Portuguese karstic springs.


  • Curriculum Armando Ribeiro

Armando Ribeiro,  diver since 1999, specialized in underwater photography and video, has won several national and international awards.The taste for deep dives, unexplored wrecks and caves, lead Armando Ribeiro to create the 1st team of technical divers that use closed circuit rebreathers (CCR) in Portugal. Created in 2004/2005 the In-Silence Dive Team has as main objectives the development of CCR diving, the exploration off deep shipwrecks and caves on the Portuguese coast and the participation in international diving expeditions. Armando quickly became one of the first serious advanced expedition divers in Portugal, taking part in numerous adventures with some of the world’s best technical divers.His most recent project aims to explore, obtain cave’s cartography and capture in video the biggest springs in Portugal. This exciting adventure was recently renewed by the discovery of new galleries that open the door to new challenges due to the greater depts and distance that can be achieved.

The expeditions and projects impact, through the publication of articles in diving magazines and the national and international public projection of their videos, had a strong recognition in the national diving community, being already a reference in all expos and events related to technical diving.

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