Asked by: Kevin Ward, Stroud

When swimming, water generates drag forces from three sources: friction from the ‘stickiness’ of water, waves created on the surface, and resistance to pushing through the water. Unless the water is so shallow that the chest of the swimmer takes up a sizeable fraction of the total depth, these sources of drag are the same for shallow or deep water, so that swimming will require the same amount of effort.

What proportion of swimming pool water is wee? © Getty Images

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Robert is a science writer and visiting professor of science at Aston University.