Marion Vollborn/ BIA / Polar Bear (Ursus maritimus) waiting at breathing hole for seals, Svalbard, Norway

Yukihiro Fukuda / Japanese giant salamander (Andrias japonicus) emerging from hole and reaching up to the surface in order to breathe, Hino River, Tottori-ken, Japan, September.

Eric Baccega / Female Harp seal (Phoca groenlandicus) surfacing at breathing hole looking at her pup, Magdalen Islands, Gulf of St Lawrence, Quebec, Canada, March.

Olga Kamenskaya / Young Baikal seal (Pusa sibirica) at breathing hole. Lake Baikal, Russia, April.

Olga Kamenskaya / Young Baikal seal (Pusa sibirica) at breathing hole. Lake Baikal, Russia, April.

Eric Baccega / Female Harp seal (Phoca groenlandicus) surfacing at a breathing hole in the sea ice, Magdalen Islands, Gulf of St Lawrence, Quebec, Canada, March 2012

Mark Brownlow / Rebreather instructor Ian Thomas and cameraman Didier Noirot prepare to dive under the ice, Lake Baikal, world's deepest and oldest (and largest by volume) freshwater lake, Siberia, Russia. BBC Plane...

Norbert Wu / Scuba diver exploring ice caves below Weddell Seal (Leptonychotes weddellii) breathing holes, life below feeds on seal feces, Antarctica

Mitsuaki Iwago / Weddell Seal (Leptonychotes weddellii) at breathing hole, Antarctica

Norbert Wu / Weddell Seal (Leptonychotes weddellii) male showing aggression towards the diver who is near breathing hole, Antarctica

Norbert Wu / Weddell Seal (Leptonychotes weddellii) breathing hole is above this ice cave with diver, the cave is filled with Sea Stars (Odontaster validus) that feeds on seal feces, Antarctica

Tui De Roy / Ringed Seal (Phoca hispida) surfacing in brash ice, Svalbard, Norwegian Arctic