

Ice divers prepare to enter the White Sea in northern Russia.
G.J. Neagle, a diver with the Sheriff's Department in Kennebec County, Maine, sits on the edge of a hole cut through 16 inches of ice while waiting to dive during a training session on Minnehonk Lake in Mt. Vernon, Maine, on Feb. 5, 2009. The early morning air temperature was minus 15 degrees F. while the water was a relatively balmy 32 degrees F.
A diver researching the sea bed is seen at O'Brien Bay, near Australia's Casey Station at Wilkes Land, Antarctica.
Ice divers swim in Reichraming, Austria, in this 2006 file photo.
Russian free diver Julia Petrik swims with beluga whales in freezing water beneath the pack ice near Murmansk. White beluga whales are an endangered species, threatened by global warming, whaling, and pollution.
Divers prepare to dive in northern Russia's White Sea.
A diver emerges from the freezing water in Russia's White Sea.
This photo provided by Push Pictures shows British explorer and endurance swimmer Lewis Gordon Pugh diving into the waters of the geographic North Pole, on July 15, 2007. Pugh Sunday braved subzero temperatures to become the first person to swim at the North Pole.
A US Coast Guard diver prepares for a dive under the ice at McMurdo Station, on Antarctica's Ross Island.
A diver checks the hull of the nuclear powered icebreaker 'Sovietsky Soyuz,' near northern Russia's Franz Josef Land.