Title The World’s Best Ultra-Deep Technical Dive Sites
June 11, 2025
For experienced technical divers, ultra-deep technical dive sites offer unique challenges and a chance to explore the planet’s most mysterious underwater realms. From secluded reefs to historic wrecks, these locations push the limits of depth and reward divers with unforgettable sights. Here is a curated list of some of the world’s top ultra-deep technical dive sites, spanning continents and offering more than just deep dives.
Top 8 Ultra-Deep Technical Dive Sites
1.The Britannic – Kea Island, Greece
Located near Athens, Kea Island is a Greek gem with rugged coastlines, crystal-clear waters, and a relaxed Mediterranean vibe. It is a perfect destination for those interested in both ancient history and technical diving. Explore ancient ruins, enjoy Greek cuisine at seaside tavernas, or take a hike along Kea’s scenic coastline.
The wreck of the HMHS Britannic, the Titanic’s sister ship, rests at around 120 meters (394 feet) and is one of the deepest and most famous wrecks accessible to technical divers. The colossal wreck, still largely intact, offers views of towering smokestacks, portholes, and even interior compartments. Strong currents and deep conditions make this a challenging but rewarding dive.
Other dive sites: Greece’s waters are home to other fascinating wrecks, including the Patris wreck, an 1868 paddle steamer lying at around 28 to 54 meters (92 to 177 feet), and several caves in nearby islands.
2. San Francisco Maru – Chuuk Lagoon, Micronesia.
Chuuk Lagoon is world-famous for its wreck diving. This remote, stunning destination in Micronesia boasts turquoise waters, lush greenery, and a warm, tropical climate. The lagoon has calm conditions, ideal for technical divers seeking a tranquil escape steeped in WWII history.
The San Francisco Maru, known as the "million-dollar wreck," sits at 64 meters (210 feet) and deeper, making it an ultra-deep dive ideal for technical wreck divers. This Japanese cargo ship is filled with wartime artifacts, including tanks, trucks, and other military equipment, now encrusted with corals. The visibility here is often exceptional, enhancing the eerie yet beautiful ambiance.
Other dive sites: Chuuk Lagoon is famous for its many WWII wrecks, including the Fujikawa Maru at 33 meters (110 feet) deep, the Reiyo Maru No.6 at approximately 67 meters (220 feet), and the Aikoku Maru, a former armed merchant cruiser at 40 to 64 meters (131 to 210 feet).
3. Blue Hole – Dahab, Egypt
Dahab, on Egypt’s Sinai Peninsula, is a small, relaxed town with a bohemian feel. Known for its breathtaking desert landscapes and vibrant reefs, it is a top destination for divers, freedivers, and adventure travelers alike. Explore the desert with a Bedouin-guided camel trek, go snorkeling in nearby lagoons, or enjoy the relaxed beachside cafes.
The Dahab Blue Hole is one of the most famous freediving and technical dive sites globally, with depths reaching over 100 meters (328 feet) in some areas. Known for the "Arch" at 56 meters (184 feet), the site presents unique challenges and incredible visibility, drawing technical divers to navigate its walls and reach ultra-deep zones.
Other dive sites: Dahab offers diverse sites such as the Canyon, a volcanic fault popular with advanced divers, and the Bells, a breathtaking wall dive. It is also a short drive from Sharm El Sheikh, one of the most popular places to go diving in Egypt.
4. SS Andrea Doria – Nantucket, USA.
Nantucket, off the coast of Massachusetts, is a picturesque New England island with cobblestone streets, lighthouses, and a rich maritime history. Known for its beautiful landscapes and seafood, it is a popular summer destination.
The Andrea Doria lies at around 73 meters (240 feet) and attracts technical divers for its depth, strong currents, and challenging conditions. This Italian luxury liner sank in 1956 and is still relatively intact, with divers able to explore its decaying halls, dining rooms, and passenger compartments.
Other dive sites: Nearby wrecks, including the U-853 German U-boat and the Empire Knight, offer challenging but rewarding dives in the area.
5. HMS Victoria – Lebanon
Lebanon offers a unique mix of Middle Eastern and Mediterranean cultures, with Beirut as a hub for history, cuisine, and vibrant nightlife. The country is dotted with ancient ruins, traditional markets, and beautiful coastal landscapes. Explore the ruins of Byblos, hike the beautiful Chouf Mountains, or enjoy the local cuisine in Beirut’s vibrant dining scene.
The wreck of the HMS Victoria, a British battleship, is unique in that it rests nearly vertical at depths up to 150 meters (492 feet). This ultra-deep dive provides a surreal experience as divers encounter the ship’s hull, superstructure, and guns in a near-upright position.
Other dive sites: Diving in Lebanon features other wrecks like the Alice B and offers stunning reefs and natural underwater arches in Batroun.
6. Boesmansgat Sinkhole – Northern Cape, South Africa.
Boesmansgat is in a remote, arid part of South Africa known for its dramatic landscapes and unique geology. This isolated area appeals to those seeking extreme adventures and an off-the-beaten-path experience.
Boesmansgat, or "Bushman’s Hole," is one of the world’s deepest sinkholes, with depths extending beyond 283 meters (928 feet). This freshwater site requires exceptional skill and preparation due to the extreme depth, temperature changes, and pitch-black conditions.
Other dive sites: Diving in South Africa also offers Aliwal Shoal, a reef known for shark diving, and Sodwana Bay, one of the country’s most colorful reef systems.
7. Ressel Cave – Lot, France
The Lot region in southwestern France is famous for its medieval villages, limestone cliffs, and serene rivers. Known for its rural charm, it is a place for divers who appreciate history and nature. Explore charming medieval towns, go wine tasting, or hike along scenic limestone cliffs and river valleys.
Ressel Cave is one of Europe’s most challenging ultra-deep cave sites, with passages extending over 2,800 meters (9,186 feet) and depths reaching beyond 80 meters (262 feet). The cave’s tunnels are narrow and intricate, making it a favorite among highly skilled full cave divers.
Other dive sites: Diving in France also offers the Fontaine de Vaucluse, a beautiful yet challenging spring dive, and several Mediterranean wrecks off the Côte d’Azur.
8. Depth Defying: The World’s Deepest Cave Dive in France
Another of France’s remarkable underwater cave systems, attracting adventure-seeking technical divers from around the globe, is the Font Estramar spring in the eastern Pyrenees, where divers push the boundaries of extreme exploration. Known for its labyrinthine tunnels and astonishing depths, this site has set the stage for record-breaking dives that redefine the limits of human endurance.
The World Record Dive: 308m into the Unknown
In 2023, Polish cave diver Krzysztof Starnawski led an expedition into the depths of Font Estramar, reaching an unprecedented depth of 308 meters (1,010 feet). This extraordinary feat surpassed previous records and reinforced the site’s status as one of the most challenging locations for deep cave diving. The dive required meticulous planning, cutting-edge equipment, and an experienced support team to ensure a safe ascent and decompression over several hours.
Other Notable Cave Diving Sites in France
While Font Estramar is now famous for the world record, France boasts several other impressive cave diving locations:
- Source de la Douix: A stunning cave with clear waters and significant depth, providing a mix of open water and overhead environments.
- Gouffre de Cabouy: Known for its long tunnels and deep passages, this cave offers a thrilling challenge for experienced divers.
Ready to take your technical diving to the next level?
Ultra-deep technical dives push the limits of human exploration and require advanced skills, precise planning, and cutting-edge equipment. If you are ready to extend your range and explore deeper, take the next step with SSI’s Extended Range programs.