Open-water swimming is one of the fastest-growing sports in the British Isles. It beats the pants – or the Speedos – off doing lengths in the municipal pools that proliferated after the Second World War. As guru figure Roger Deakin wrote in his popular book Waterlog, river swimming provides an escape from "endlessly turning back on myself like a tiger pacing its cage". It's an opportunity to discover your inner tiger (no, not that one), to get back to nature or, in the case of skinny-dipping, back to naturism. As it did for the Victorians and Edwardians, it provides respite from rampant industrialisation. Unless, that is, you swallow a mouthful of factory discharge while getting your feet tangled up in a shopping trolley.
In Wild Swimming (BBC4, Tuesday), there were no such dangers as Alice Roberts took her unborn child on a tour of Britain's aquatic beauty spots, but there were still a few submerged fears. It was a journey deep down inside as much as it was an appreciation of the natural world. For water is "the source of life" but it's also the shadowy realm, an alien environment.
A rather bonkers Professor Ronald Hutton, an expert on Hadrian's Wall, pointed out that water has provided a metaphor for so many of our emotional responses, both good and bad, whether you are pouring your heart out or just going with the flow. So when Deakin wrote about getting "under the skin" of nature rather than just looking at the surface, he may have been talking literally, but you are also getting under your own skin. Poets and painters have celebrated the beauty of water, but they have always drunk deep from the well of watery inspiration in order to explore the human condition.
In The Man Who Swam to Scotland (BBC4, Tuesday), Frank Chalmers was getting under his wife's skin rather than his own. He wanted to be the first man to swim from the Orkney Islands to mainland Scotland, but it's a stretch of water beset by tidal swirls and she had to sit in a caravan for two weeks until the local fisherman Mungo would give Chalmers the all-clear.
He had to be fished out before he could complete the swim, and sadly his response to the failure was drowned out by music. He revealed he kept himself going in the harsh conditions by singing songs in his head that he had written himself; a case of sink or sing. Mercifully, perhaps, these songs were also drowned out by the swelling score.
You don't need to devise songs to keep your morale up in Britain's 1,000 lakes and 8,000 rivers. They bubble up of their own accord as you glide along. Dr Roberts didn't even get her hair wet. She finally got naked in the Lake District and said, "You don't just feel close to nature, you feel part of it". When her waters break, her Water Baby had better be ready for a pretty chilly birthing pool.