What is it? A pursuit where you get into some water, sort of flail around for a bit and then get out again.

How much does it cost? Sometimes a few quid, sometimes included in a gym membership, sometimes free if you’re either a billionaire with your own pool or the sort of reckless idiot who enjoys swimming in the sea.

What does it promise? A whole catalogue of benefits. Swimming is one of the best activities for full-body toning, plus it can massively increase your flexibility and lung capacity.

What’s it actually like? I am a lapsed swimmer. Until this week, the last time I swam was in the sea on holiday, and that came to a sudden end when something under the surface nudged my foot and I freaked out. Since then, I’ve apparently got quite bad at swimming. Three breaststroked lengths of my local leisure centre’s pool was enough to legitimately exhaust me, while an array of middle-aged ladies patiently went backwards and forwards without a break for what seemed like hours. But it’s worth persevering; a few adult lessons were enough to turn my brother from a strident non-swimmer to someone who now competes in triathlons. (Swimming.org is a good place to start.) I’m not anywhere near that level, but I’d like to improve my technique.

Best and worst bit Catch the pool on a quiet day and swimming offers a tranquillity you just don’t get with other workouts. The worst bits are all the other people you have to zigzag around and, if you’re swimming in the sea, the evil creatures that insist on nudging your foot and freaking you out.

Is it worth it? Yes.