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Fish floats

Duration: 01:17

To stop sinking, fish needed the equivalent of buoyancy tanks on a submarine. Less gas and we sink, more and we rise. But whereas a sub uses compressed air, a fish must carry its gas supply in its bloodstream. For this, fish have an onboard float - the swim-bladder that is a large gas-filled sac that inflates and deflates as needed. Gas diffuses back and forth between the swim-bladder and the bloodstream, letting fish float effortlessly at any depth. Despite being heavy boned the fish is, in effect, weightless.

Available since: Mon 14 Feb 2011



This clip is from

Journey of Life SEAS OF LIFE

Steve Leonard explores the oceans & traces the story of life's origins from microbes to the the blue whale, the largest animal that ever lived.

First broadcast: 13 Apr 2005

Image for SEAS OF LIFE Not currently available on BBC iPlayer

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