The world's underwater caves: how far they run and how deep they go
71 cave systems26 countries1,379 km of surveyed passage24 with published maps
The world's flooded caves as their survey teams have published them: how far each has been mapped and how deep, who mapped it, its entrances and who controls access. Every figure links to its source and carries the date it was published.
Satellite: NASA Blue Marble
47 systems on the map. Click a dot to open its page; hollow dots mark an approximate position. For orientation, not navigation. 24 more have no published position yet and are listed below.
Records
The longest underwater caves yet surveyed
| # | System | Surveyed length |
|---|---|---|
| 1 | Sistema Ox Bel HaMexico · Quintana Roo | 496.8 km2024-10 |
| 2 | Sistema Sac ActunMexico · Quintana Roo | 379.6 km2024-12 |
| 3 | Sistema K'oox BaalMexico · Quintana Roo | 103.1 km2024-04 |
| 4 | Wakulla-Leon Sinks cave systemUnited States · Florida | 72.2 km2023-01-07 |
| 5 | Sistema Xunaan HaMexico · Quintana Roo | 57.3 km2024-04 |
| 6 | Sistema Toh HaMexico · Quintana Roo | 47.7 km2018-12 |
| 7 | Dan's Cave SystemThe Bahamas · Abaco | 19.3 km2026-07 |
| 8 | Blauhöhle system (Blautopf)Germany · Baden-Württemberg | 19.0 km2026-10 |
| 9 | Grotte del Bue MarinoItaly · Sardinia (Nuoro) | 15.0 km |
| 10 | Sistema Dos PisosMexico · Quintana Roo | 14.8 km2019-11 |
Underwater passage as last published by the survey teams; their lists are updated as exploration continues. Systems with no published length are left out.
Records
The deepest flooded caves yet explored
| # | System | Depth |
|---|---|---|
| 1 | Hranice AbyssCzechia · Sinkhole | 521 m |
| 2 | Pozzo del MerroItaly · Sinkhole | 392 m |
| 3 | Långban MineSweden · Flooded mine | 365 m |
| 4 | Fontaine de VaucluseFrance · Resurgence | 315 m |
| 5 | BoesmansgatSouth Africa · Sinkhole | 283 m |
| 6 | Harasib CaveNamibia · Underwater cave | 265 m |
| 7 | Ojamo MineFinland · Flooded mine | 250 m |
| 8 | Pearse ResurgenceNew Zealand · Resurgence | 245 m |
| 9 | Gouls de TourneFrance · Resurgence | 240 m |
| 10 | Lagoa MisteriosaBrazil · Sinkhole | 220 m |
The deepest point known in the flooded cave, often reached by a robot or ROV rather than a diver. Each system page says how and when it was measured.
Browse
Every cave system, by country, type and access
Anchialine cave · 13Underwater cave · 13Sinkhole · 12Spring system · 12Resurgence · 11Blue hole · 5Flooded mine · 4Sea cave · 1
Open to qualified divers
Australia 4The Bahamas 5Belize 1Brazil 5Czechia 1Dominican Republic 2Egypt 1Finland 1France 6Germany 1Greece 1Hungary 2Italy 2Mexico 10Namibia 4New Zealand 1Norway 1Philippines 2Portugal 1Slovenia 1South Africa 2Spain 2Sweden 2United Kingdom 2United States 10Zimbabwe 1
Published maps
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
| Green Waterhole - Tank Cave systemSouth Australia | Underwater cave | 10.0 km | — | 2 | Varies by entrance | |
| Cocklebiddy CaveWestern Australia | Underwater cave | 6.3 km1995 | — | 1 | Restricted access | |
 |
Engelbrecht CaveSouth Australia | Underwater cave | — | 22 m | 2 | Open to qualified divers, with conditions |
| Piccaninnie Ponds Karst WetlandsSouth Australia | Spring system | — | 110 m | 1 | Closed to diving |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
| Dan's Cave SystemAbaco | Anchialine cave | 19.3 km2026-07 | 60 m | 2 | Restricted access | |
 |
Lucayan CavernsGrand Bahama | Anchialine cave | 10.5 km | — | 1 | Varies by entrance |
 |
Dean's Blue HoleLong Island | Blue hole | — | 202 m | 1 | Access status not verified |
| Sawmill SinkAbaco | Blue hole | — | 54 m | 1 | Restricted access | |
| Stargate Blue HoleSouth Andros | Blue hole | — | 104 m | 1 | Private: owner permission required |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
| Great Blue HoleLighthouse Reef Atoll | Blue hole | — | 125 m | 1 | Open to qualified divers, with conditions |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
 |
Abismo AnhumasMato Grosso do Sul | Sinkhole | — | 80 m | 1 | Open to qualified divers, with conditions |
 |
Gruta do Lago AzulMato Grosso do Sul | Underwater cave | — | 90 m | 1 | Restricted access |
| Gruta do MimosoMato Grosso do Sul | Underwater cave | — | — | 1 | Open to qualified divers, with conditions | |
 |
Lagoa MisteriosaMato Grosso do Sul | Sinkhole | — | 220 m | 1 | Open to qualified divers, with conditions |
| Poço AzulBahia | Sinkhole | — | 60 m | 1 | Access status not verified |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
| Hranice AbyssOlomouc Region | Sinkhole | — | 521 m | 1 | Restricted access |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
| Manantial de la AletaLa Altagracia | Sinkhole | — | 73 m | 1 | Access status not verified | |
| Padre Nuestro ComplexLa Altagracia | Sinkhole | — | — | 1 | Open to qualified divers, with conditions |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
 |
Blue Hole (Dahab)South Sinai | Blue hole | — | — | 1 | Open to qualified divers, with conditions |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
 |
Ojamo MineUusimaa | Flooded mine | — | 250 m | 1 | Restricted access |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
| Émergence du ResselLot (Occitanie) | Resurgence | 5.9 km2005 | 78 m | 1 | Open to qualified divers, with conditions | |
| Font del TruffeLot (Occitanie) | Resurgence | — | 30 m | 1 | Access status not verified | |
 |
Fontaine de VaucluseVaucluse (Provence-Alpes-Côte d'Azur) | Resurgence | — | 315 m | 1 | Restricted access |
 |
Gouls de TourneArdèche (Auvergne-Rhône-Alpes) | Resurgence | — | 240 m | 2 | Open to qualified divers, with conditions |
| Réseau de l'Ouysse (Cabouy – Pou Meyssen)Lot (Occitanie) | Resurgence | — | — | 2 | Access status not verified | |
| Source de Saint-SauveurLot (Occitanie) | Resurgence | — | 195 m | 1 | Restricted access |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
 |
Blauhöhle system (Blautopf)Baden-Württemberg | Underwater cave | 19.0 km2026-10 | — | 1 | Restricted access |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
 |
Maaras resurgence (Aggitis Cave)Drama (Eastern Macedonia and Thrace) | Resurgence | 11.8 km2010-08 | 68 m | — | Restricted access |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
 |
Molnár János CaveBudapest | Underwater cave | 6.2 km2025-12-31 | — | 1 | Open to qualified divers, with conditions |
 |
Tapolca cave system | Underwater cave | — | — | — | Restricted access |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
 |
Grotte del Bue MarinoSardinia (Nuoro) | Sea cave | 15.0 km | — | 1 | Varies by entrance |
 |
Pozzo del MerroLazio | Sinkhole | — | 392 m | 1 | Restricted access |
10
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
| Sistema Ox Bel HaQuintana Roo | Anchialine cave | 496.8 km2024-10 | 57 m | 1 | Varies by entrance | |
 |
Sistema Sac ActunQuintana Roo | Anchialine cave | 379.6 km2024-12 | 119 m | 6 | Varies by entrance |
| Sistema K'oox BaalQuintana Roo | Anchialine cave | 103.1 km2024-04 | 26 m | 1 | Varies by entrance | |
 |
Sistema Xunaan HaQuintana Roo | Anchialine cave | 57.3 km2024-04 | 27 m | — | Access status not verified |
| Sistema Toh HaQuintana Roo | Anchialine cave | 47.7 km2018-12 | 13 m | 1 | Access status not verified | |
| Sistema Dos PisosQuintana Roo | Anchialine cave | 14.8 km2019-11 | 24 m | — | Access status not verified | |
| Cueva QuebradaQuintana Roo | Anchialine cave | 11.6 km2014-07 | 9 m | — | Restricted access | |
| Sistema Taj MahalQuintana Roo | Anchialine cave | 10.0 km2017-08 | 24 m | 1 | Open to qualified divers, with conditions | |
| Sistema Chac-MolQuintana Roo | Anchialine cave | 9.2 km2000-01 | 28 m | 2 | Open to qualified divers, with conditions | |
 |
Sistema CarwashQuintana Roo | Anchialine cave | 3.2 km2016-09 | 26 m | 1 | Open to qualified divers, with conditions |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
| Dragon's Breath CaveOtjozondjupa | Underwater cave | — | 205 m | 1 | Private: owner permission required | |
| Harasib CaveOtjozondjupa | Underwater cave | — | 265 m | — | Private: owner permission required | |
 |
Lake GuinasOshikoto | Sinkhole | — | 133 m | 1 | Private: owner permission required |
 |
Lake OtjikotoOshikoto | Sinkhole | — | — | 1 | Restricted access |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
| Pearse ResurgenceTasman | Resurgence | — | 245 m | 1 | Access status not verified |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
 |
Pluragrotta–Steinugleflåget systemNordland | Underwater cave | 2.6 km2026 | 130 m | 2 | Open to qualified divers, with conditions |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
| Pawod Underwater Cave SystemCebu (Central Visayas) | Underwater cave | 258 m2016-05 | — | 1 | Access status not verified | |
 |
Hinatuan Enchanted River Underwater Cave SystemSurigao del Sur (Caraga) | Spring system | — | — | 1 | Access status not verified |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
 |
Olhos de Água do AlvielaCentral Portugal (Planalto de Santo António) | Resurgence | — | 125 m | — | Access status not verified |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
 |
Divje jezeroIdrija | Spring system | — | 160 m | 1 | Closed to diving |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
| BoesmansgatNorthern Cape | Sinkhole | — | 283 m | 1 | Private: owner permission required | |
| Komati SpringsMpumalanga | Flooded mine | — | 186 m | 1 | Access status not verified |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
 |
Sistema Gleda–Camp des PouMallorca (Balearic Islands) | Anchialine cave | 14.6 km2020 | 24 m | 2 | Restricted access |
 |
Pozo AzulBurgos (Castilla y León) | Resurgence | 13.7 km2015-08 | 71 m | 1 | Access status not verified |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
 |
Tuna-Hästberg Mine (Äventyrsgruvan)Dalarna | Flooded mine | 7.0 km2026 | — | 1 | Open to qualified divers, with conditions |
| Långban MineVärmland | Flooded mine | — | 365 m | 1 | Restricted access |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
 |
Wookey HoleSomerset | Underwater cave | 3.7 km2024-03-02 | 143 m | — | Private: owner permission required |
 |
Kingsdale system (Keld Head)Yorkshire Dales | Resurgence | — | — | 2 | Varies by entrance |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
| Wakulla-Leon Sinks cave systemFlorida | Spring system | 72.2 km2023-01-07 | — | 4 | Varies by entrance | |
 |
Peacock Springs cave systemFlorida | Spring system | 10.1 km2026-03 | — | 2 | Open to qualified divers, with conditions |
 |
Manatee Springs cave systemFlorida | Spring system | 8.0 km | — | 3 | Open to qualified divers, with conditions |
 |
Madison Blue Spring cave systemFlorida | Spring system | 7.9 km2014 | — | 2 | Open to qualified divers, with conditions |
 |
Jacob's Well caveTexas | Spring system | 1.8 km | 42 m | 1 | Closed to diving |
| Cow Springs caveFlorida | Spring system | — | — | 1 | Restricted access | |
| Devil's Spring System (Ginnie Springs)Florida | Spring system | — | — | 3 | Open to qualified divers, with conditions | |
| Eagle's Nest Sink caveFlorida | Sinkhole | — | 94 m | 1 | Open to qualified divers, with conditions | |
| Jackson Blue Spring caveFlorida | Spring system | — | — | 1 | Access status not verified | |
| Little River Springs caveFlorida | Spring system | — | — | 1 | Open to qualified divers, with conditions |
| System | Type | Surveyed length | Depth | Entrances | Access | |
|---|---|---|---|---|---|---|
 |
Chinhoyi CavesMashonaland West | Sinkhole | — | 103 m | 1 | Open to qualified divers, with conditions |
Maps
Published maps and surveys
For orientation only. Maps here and on the linked sites are not underwater navigation tools. Cave surveys belong to the teams that drew them; respect their copyright and publication restrictions.
| Map or survey | Publisher | System |
|---|---|---|
| QRSS: Underwater caves of Isla Cozumel ↗Cozumel cave list and access notes. | Quintana Roo Speleological Survey | Cueva Quebrada |
| Divje jezero (fiche with section and plan) ↗Fiche by Frank Vasseur with bibliography of Slovenian sources. | plongeesout.ffspeleo.fr | Divje jezero |
| Font del Truffe (fiche with section, plan, S12 plan and terminal sketch) ↗Fiche by F. Vasseur, updated 16 March 2016. | plongeesout.ffspeleo.fr | Font del Truffe |
| Goul de la Tannerie (fiche with sections and plans) ↗After documents by Bertrand Léger, updated by F. Vasseur. | plongeesout.ffspeleo.fr | Gouls de Tourne |
| Goul du Pont (fiche with plan and sections) ↗Fiche by F. Vasseur, updated 2 November 2007. | plongeesout.ffspeleo.fr | Gouls de Tourne |
| Mapy (maps of the abyss) ↗Published maps and current-state section of the research group's site. | ZO ČSS 7-02 Hranický kras | Hranice Abyss |
| Expédition 2010 – Le karst du massif du Falakro et la résurgence de Maaras (report with survey 1978-2010) ↗Hydrogeological and survey results. | Pascal Reilé (FFS), hosted on plongeesout.ffspeleo.fr | Maaras resurgence (Aggitis Cave) |
| Research report on the 2025 research of the Molnár János Cave (in Hungarian) ↗Includes a survey-line excerpt of the 2025 extension; not a full cave map. | termeszetvedelem.hu (Hungarian nature conservation portal) | Molnár János Cave |
| Olhos de Agua do Alviela (fiche with survey) ↗Links to a survey drawing and the expedition account. | plongeesout.ffspeleo.fr | Olhos de Água do Alviela |
| Pozzo del Merro – cave sheet (I Monti Cornicolani) ↗Regional cave register sheet with description and history (catasto La 32). | Parchi Lazio | Pozzo del Merro |
| Résurgence de Cabouy (fiche with plan and section of Cabouy–Pou Meyssen) ↗Links to Cabouy–Pou Meyssen plan and section and a complete plan of the Ouysse network dated December 2017. | plongeesout.ffspeleo.fr | Réseau de l'Ouysse (Cabouy – Pou Meyssen) |
| Gouffre de Pou Meyssen (fiche) ↗Updated 29 November 2014 with surveys proposed by Torsten Schnitter; links to upstream plans. | plongeesout.ffspeleo.fr | Réseau de l'Ouysse (Cabouy – Pou Meyssen) |
| QRSS list of long underwater caves in Quintana Roo ↗Length, depth and cenote count table. | Quintana Roo Speleological Survey | Sistema Carwash |
| QRSS list of long underwater caves in Quintana Roo ↗Length, depth and cenote count table. | Quintana Roo Speleological Survey | Sistema Chac-Mol |
| QRSS list of long underwater caves in Quintana Roo ↗Length, depth and cenote count table. | Quintana Roo Speleological Survey | Sistema Dos Pisos |
| Sistema Gleda-Camp des Pou (Manacor, Mallorca): estat de la qüestió ↗Open-access review with historical and current survey figures (CC BY-NC-ND 4.0). | Societat Espeleològica Balear (Papers SEB 3, 2020) | Sistema Gleda–Camp des Pou |
| QRSS list of long underwater caves in Quintana Roo ↗Length, depth and cenote count table. | Quintana Roo Speleological Survey | Sistema K'oox Baal |
| CINDAQ annual reports ↗Yearly reports with survey totals and project summaries. | CINDAQ | Sistema Ox Bel Ha |
| QRSS list of long underwater caves in Quintana Roo ↗Length, depth and cenote count table. | Quintana Roo Speleological Survey | Sistema Ox Bel Ha |
| QRSS list of long underwater caves in Quintana Roo ↗Length, depth and cenote count table; QRSS sells printed maps separately. | Quintana Roo Speleological Survey | Sistema Sac Actun |
| QRSS list of long underwater caves in Quintana Roo ↗Length, depth and cenote count table. | Quintana Roo Speleological Survey | Sistema Taj Mahal |
| QRSS list of long underwater caves in Quintana Roo ↗Length, depth and cenote count table. | Quintana Roo Speleological Survey | Sistema Toh Ha |
| QRSS list of long underwater caves in Quintana Roo ↗Length, depth and cenote count table. | Quintana Roo Speleological Survey | Sistema Xunaan Ha |
| Source de Saint Sauveur (fiche with section 2005 and plan) ↗Links to a 2005 section, a plan and a section of the Vierge Noire gallery. | plongeesout.ffspeleo.fr | Source de Saint-Sauveur |
| Wakulla Basin Mapping Initiative - Update 2 ↗Expedition update (2026-08-04) on 3D mapping with an autonomous vehicle and radio location of passages; no map is... | Woodville Karst Plain Project | Wakulla-Leon Sinks cave system |
| Mendip Cave Registry entry: Wookey Hole ↗Registry record listing 28 historic surveys (1904-1969). | Mendip Cave Registry & Archive | Wookey Hole |
| RESSEL mise à jour / update: complete survey (2005) ↗Plans and sections of each part of the cave, survey by HFGK, INGO and the Landesverein für Höhlenkunde in der... | plongeesout.ffspeleo.fr | Émergence du Ressel |
| Cave Areas of Quintana Roo (QRSS cave footprint map) ↗An area-level map of known cave zones around Tulum, built by buffering survey lines by 250 m. It shows how much of... | Quintana Roo Speleological Survey | — |
| Hoyo Negro Project ↗Project site for the Hoyo Negro research: Naia, the extinct fauna, digital documentation by photogrammetry, and a... | Instituto Nacional de Antropología e Historia / University of California San Diego | — |
| Karst Underwater Research (KUR) ↗A volunteer non-profit exploring and documenting flooded karst in Florida, including Manatee, Madison, Ichetucknee,... | Karst Underwater Research | — |
| Karst in the United States: A Digital Map Compilation and Database ↗A national GIS and KML map of rocks and deposits that host or could host karst in the US, Puerto Rico and the US... | U.S. Geological Survey (Open-File Report 2014-1156) | — |
| New Madison and Manatee cave maps ↗Announcement of updated survey maps of Madison Blue Spring and Manatee Springs in Florida, with free small-scale... | Karst Underwater Research | — |
| Proyecto Espeleológico Sistema Huautla (PESH) ↗The exploration project for Sistema Huautla in Mexico, a very deep cave system whose flooded sections have been the... | PESH | — |
| Quintana Roo Speleological Survey (QRSS) ↗A long-running project that gathers cave survey data for Quintana Roo, Mexico. It publishes length and depth... | Quintana Roo Speleological Survey | — |
| U.S. Deep Caving Team ↗A non-profit devoted to exploring the planet's remaining frontiers and building the technology to do it. Its... | U.S. Deep Caving Team, Inc. | — |
| Woodville Karst Plain Project (WKPP) ↗A non-profit exploring and studying the flooded caves of North Florida's Woodville Karst Plain, including the... | Woodville Karst Plain Project | — |
| World Karst Aquifer Map (WOKAM) ↗A global map of potential karst aquifers in carbonate and evaporite rocks, with selected major karst springs and... | WHYMAP / Federal Institute for Geosciences and Natural Resources (BGR) | — |