Sue Flood / Swimming pool at Olarro, private lodge in Loita Hills, over Greater Masai Mara towards Tanzania, Kenya September 2011

Paul Williams / Yacare caiman (Caiman yacare) - at the end of the wet season large numbers of Caiman are attracted to drying pools to feed on the trapped fish, Pantanal, Pocone, Brazil, August

Inaki Relanzon / Small island with luxury houses and swimming pools. Florida Keys, Florida, USA, April 2006.

Nick Upton / Tourists bathing in pools in the Krka river below Skradinski buk waterfalls, Krka National Park, Sibenik, Croatia, July 2010.

Laurent Geslin / Common / Moorish gecko (Tarentola mauritanica) on statue at night, south of France, July 2010

Bryan and Cherry Alexander / Bathers swimming during February in hole in ice covering Lake Semyonovskaya. Murmansk, Northwest Russia, 2005.

Toby Roxburgh / Henleaze Lake, a former quarry and now spring-fed outdoor swimming and high-diving facility, Bristol, England, UK, 2009.

David Kjaer / Man swimming in mountain pool at foot of waterfall, Glen Coe, Scotland, June 2009

Wild Wonders of Europe / Relanzón / Waves breaking on rocky shore, creating natural swimming pools, El Charco azul, near Puerto Espindola, La Palma, Canary Islands, Spain, March 2009

Inaki Relanzon / Bathers relaxing in The Blue Lagoon, Thermal area and swimming pools on the Reykjanes Peninsula, near Reykjavik, Iceland

Inaki Relanzon / Bathers relaxing in The Blue Lagoon, Thermal area and swimming pools on the Reykjanes Peninsula, near Reykjavik, Iceland

Michael Durham / Gemfish (Atractosteus spatula) underwater portrait, they inhabit sluggish pools and brackish water in southeastern United States and Mexico