Divers going into the Chimney at Sail Rock, Koh Tao, Thailand, Southeast Asia, Asia

Diver inside the wreck of the Lesleen M freighter, sunk as an artificial reef in 1985 in Anse Cochon Bay, St. Lucia, West Indies, Caribbean, Central America

Scunba diver and reef, Southern Thailand, Thailand, Andaman Sea, Indian Ocean, Asia

Diver swimming along a wall at Bunaken, Sulawesi, Indonesia, Southeast Asia, Asia

Diver swimming along a wall at Bunaken, Sulawesi, Indonesia, Southeast Asia, Asia

Hawksbill turtle (Eretmochelys imbricata) and diver, Sulawesi, Indonesia, Southeast Asia, Asia

Diver and green turtle (Chelonia mydas), Sulawesi, Indonesia, Southeast Asia, Asia

Diver swimming through a school of fish, Thailand, Southeast Asia, Asia

A gorgonian sea fan (possibly Echinogorgia species) octocoral on a tropical coral reef, in Gaafu Dhaalu atoll, The Maldives, Indian Ocean, Asia

A myriad of hard and soft corals, as well as tropical reef fish on the healthy reef near Volivoli Resort on Viti Levu, Fiji, South Pacific, Pacific

Snorkeler with golden jellyfish (Mastigias papua etpisoni), in Jellyfish Lake, a marine lake located on Eil Malk island, Rock Islands, Palau, Micronesia, Pacific

Whale shark (Rhincodon typus), underwater with snorkeler on Ningaloo Reef, Western Australia, Australia, Pacific

Whale shark (Rhincodon typus), underwater with snorkelers on Ningaloo Reef, Western Australia, Australia, Pacific

Whale shark (Rhincodon typus), underwater with snorkeler on Ningaloo Reef, Western Australia, Australia, Pacific

Whale shark (Rhincodon typus), underwater with snorkeler on Ningaloo Reef, Western Australia, Australia, Pacific

Whale shark (Rhincodon typus), underwater with snorkeler on Ningaloo Reef, Western Australia, Australia, Pacific

An adult hawksbill turtle (Eretmochelys imbricata), with photographer on Sauwaderek Village Reef, Raja Ampat, Indonesia, Southeast Asia, Asia

Adult dwarf minke whale (Balaenoptera acutorostrata), with snorkeler, Great Barrier Reef, Queensland, Australia, Pacific

A diver around a Stylophora species hard coral, on a tropical coral reef, in Gaafu Dhaalu atoll, The Maldives. Indian Ocean, Asia

Adult dwarf minke whale (Balaenoptera acutorostrata), underwater with snorkeler near Ribbon 10 Reef, Great Barrier Reef, Queensland, Australia, Pacific

Adult dwarf minke whale (Balaenoptera acutorostrata) with snorkelers near Ribbon 10 Reef, Great Barrier Reef, Queensland, Australia, Pacific

Interior of British Blockship Doyle, Scapa Flow, Orkney islands, Scotland, UK

Diver inside British Blockship Doyle, Scapa Flow, Orkney islands, Scotland, UK

Diver swimming through cavern with torch, Grand Cayman Island, Cayman Islands, Caribbean

Split View of a teenage girl snorkeling in a bikini with a tour boat on the surface of the water above, Country of Aruba

Young snorkeler dives toward coral in the Buccoo Reef and Nylon Pool, Tobago, Tobago, Republic of Trinidad and Tobago

Young woman snorkeling with a school of fish, Water Cay, Utila, Honduras

An aerial view of Balicasag Island, a tiny island in South West Bohol in the central Philippines. It is famous for scuba diving on the deep, vertical walls and there are some fantastic hard coral gardens at snorkeling depths, Balicasag Island, Philippines

Divers on a WW II Corsair fighter plane off Southeast Oahu, Oahu, Hawaii, United States of America

An aerial view of the live aboard vessel Infiniti for scuba diving off Balicasag Island, a tiny island in South West Bohol in the central Philippines. It is famous for scuba diving on the deep, vertical walls and there are some fantastic hard coral gardens at snorkeling depths, Balicasag Island, Philippines

Three young people free diving over a Hawaiian reef, Hawaii, United States of America

A young couple free diving in clear water over a Hawaiian reef, Hawaii, United States of America

Hawaii, Maui, Lahaina, Atlantis submarine visits the Carthaginian, sunk as an artificial reef December 2005

Young woman in red bikini snorkels over coral reef, Molokini, Hawaii, United States of America

A split scene with a shallow hard coral reef below water and island above with the live aboard dive vessel Infiniti, Philippines

Divers exploring the prop and rudder at the stern of The Carthaginian, a Lahaina landmark, that was sunk as an artificial reef off Lahaina, Maui, Hawaii in December 2005, Maui, Hawaii, United States of America

The Backwall at Molokini Marine Preserve drops down to 300 feet. Various reef fish stick close to a crevice here, Molokini, Maui, Hawaii, United States of America