Top 10 Biggest Underwater Caves

Located in Georgia, Krubera Cave is considered the largest underwater cave system in the world, spanning over 8 km (5 miles) beneath the Black Sea. The cave's entrance was discovered in 1964 and has since been explored by only a handful of expeditions. With an average depth of 130 meters (430 feet), it provides a challenging environment for divers to navigate through. This cave has never been fully mapped, making it one of the most extensive underwater cave systems.

Situated on the Caribbean coast of Mexico's Yucatan Peninsula, the Sistema Sac Actun is the largest underwater cave system in the Americas and second-largest in the world, covering an area of approximately 5 km² (1.9 mi²). It features over 300 kilometers of underwater passages and numerous ancient Mayan artifacts, providing valuable insights into the region's history. The cave has been a popular destination for scuba diving tours since the 1990s.

While not exclusively underwater, a portion of Vietnam's Hang Son Doong Cave is submerged in water, making it one of the most impressive and unique natural formations worldwide. The world's largest cave was first discovered in 1991 by local villagers but gained international attention when it was officially recognized as a UNESCO World Heritage Site in 2015. It has been explored by only a handful of expeditions.

Located on the coast of Kyushu, Japan, the Noto Cave is one of the largest underwater cave systems in the country and features over 3 kilometers of underwater tunnels. The system was first discovered in the 1960s and has since been explored by divers from around the globe. Its unique geological formations make it a fascinating destination for scientific research.

Another natural wonder found in Vietnam, this massive cave system stretches over 250 meters (820 feet) underground and covers an area of approximately 800 square meters. The unique formations within the cave have earned it the nickname "Hell's Gate" due to its resemblance to a volcanic crater. Due to its remote location, very few people have ventured into Hang Nga Cave.

Situated in the state of Tamaulipas, Mexico, the Capuchin Cave is known for its remarkable fossil finds and features several underwater passages totaling over 2 km (1.24 miles) in length. Discovered by local divers in the early 2000s, it remains an essential destination for scientific research into ancient marine life.

Located off the coast of Belize, Central America, this stunning natural sinkhole is a popular dive site and features several underwater caves with depths reaching as low as 50 meters (164 feet). Formed thousands of years ago, the collapse of the sea floor created the Blue Hole's distinctive appearance. The surrounding ecosystem supports a diverse array of marine life.

In the southern part of Vietnam, specifically on the island of Ho Chi Minh, lies the impressive Tho Chu Cave system. Spanning an area of over 1.4 km² (0.54 mi²), it features numerous underwater caves and vast saltwater lakes with depths ranging from 10 to 30 meters. The cave system has been explored by local divers but remains relatively uncharted due to its remote location.

Found on Mexico's popular tourist island of Cozumel, the Santo Tomas Cave is a favorite among scuba divers due to its numerous underwater passages and large, saltwater lake within the cave system. The cave was discovered by Mexican researchers in 1991, and since then, it has been extensively explored for its marine life and formations.

This remote underwater cave located off the coast of Mexico's Yucatan Peninsula offers a breathtaking dive experience with its diverse marine life and numerous underground caverns and tunnels. Spanning an area of about 1.5 km² (0.58 mi²), the cave system features depths ranging from 10 to 20 meters, providing divers with a unique underwater adventure amidst beautiful natural formations.