David Fleetham / Humpback whale (Megaptera novaeangliae), mother and calf swimming just below surface in front of the West Maui Mountains. South of Lahaina, West Maui, Hawaii.

David Fleetham / Blacktip reef shark (Carcharhinus melanopterus) swimming just below surface at sunset, split level view. Off the island of Yap, Micronesia.

David Fleetham / Green Sea Turtle (Chelonia mydas) below surf instructor Tara Angioletti on a stand-up paddle board off Canoe Bearch, Maui, Hawaii. Model released.

Juergen Freund / Banded sea kraits (Laticauda colubrina) around the roots of mangrove tree, split level. Mali Island, Macuata Province, Fiji, South Pacific.

Michael Pitts / Lake Assal shoreline - Africas lowest point at 515 feet below sea level, Djibouti, , March 2008

Bryan and Cherry Alexander / Tabular iceberg showing the portion underwater that is sculpted by the sea. Polar regions. Digitally created image composite

Bryan and Cherry Alexander / Ice arch iceberg showing the portion underwater that is sculpted by the sea. Polar regions. Digitally created image composite

Doug Allan / Humpback whale (Megaptera novaeangliae) swimming below a whale watching boat, Sue Flood, photographer in boat, Vava'u, Kingdom of Tonga, South Pacific, September 2006, Model released

Chadden Hunter / Dallol hot springs where water heated by magma laden with potassium, sulphur and iron spews up through salt pans staining the salt deposits with vivid colours, in the bottom of the Rift Valley, 120 me...

Marguerite Smits Van Oyen / Lac Assal, crystallised salt on shoreline, 150m below sea level. Djibouti, East Africa sea water

Alex Mustard / Split level image of hard coral garden flourishing in shallow water below Misool Eco Resort. Misool, Raja Ampat, West Papua, Indonesia. Ceram Sea. Tropical West Pacific Ocean.

David Fleetham / Woman on stand-up paddle board with two curious Humpback whales (Megaptera novaeangliae) in water below. Maui, Hawaii. October 2010. Model released. Digital composite.