The format could not be simpler. Run to water. Get in. Run home slightly colder and considerably happier. No entry fee, no timing chip, no result to report, and no way to do it badly.
It does, however, expose your kit in a way nothing else does, because everything you are wearing is about to be soaked and then asked to keep working for another forty minutes. Kit that is merely sweat-tolerant is not the same as kit that has been fully submerged.
Shorts that drain
This is the whole thing. A short with a liner that holds water will chafe on the way home, guaranteed. You want a woven outer that sheds rather than absorbs, and pockets that let water out rather than carrying half a litre of lake back with you. A short that has been swum in should feel close to dry within ten minutes of running.
A top you can wring out
Lightweight knit, nothing heavy, nothing cotton. If it doubles as something you can swim in without feeling absurd, better still. A singlet is the obvious answer here, and it dries faster than anything with sleeves.
Something on your head
A cap that packs flat so it can go in a waistband while you are in the water, or a bucket if the sun is high and the run back is exposed. Either way, something that does not mind being damp. Avoid anything with structure that water will collapse.
One thing you will forget
Somewhere dry for a key. A zipped internal pocket is the difference between a relaxed swim and twenty minutes of standing in waist-deep water patting yourself down. A small dry bag solves it permanently and weighs nothing.
And the rule
Check the water before you commit, go in with someone, and do not jump into anything you have not looked into first. Cold water does strange things to your breathing for the first thirty seconds, so get in rather than dive in, and give yourself a moment before you start swimming. The run home is better when nobody has had a fright.
Swim-friendly shorts and light layers are in Summer Nights and Shorts.
