Every year the men's swim short cycles between two errors, and every year a great many men select one of them with total confidence. Too long and you are a teenager at a water park; too short and you are a Riviera character actor working without a script.

The number is 15 to 18 centimetres of inseam for most men, landing mid-thigh, roughly a hand's width above the knee. This is not a matter of taste. It is a proportional relationship between the leg and the garment, and it holds whether you are 175cm or 195cm because the reference point is your thigh and not the floor. These are facts. Facts I tell you!

Fabric has quietly improved while nobody was paying attention. Recycled polyamide dries in about 20 minutes against 90 minutes for the polyester blends of a decade ago, which is the difference between lunch and a damp chair. Look for a stated weight around 120 to 150 gsm; lighter than that and the short becomes transparent in water, which is a lesson best learned in a private pool. Or not at all.

Pattern is where restraint pays. A solid colour, a fine stripe or a small repeating motif that you cannot identify from four metres will all work indefinitely. Anything with a large printed image is a garment with an expiry date, and the date is the end of this summer.

I own three pairs, all solid, in navy, a faded olive and a red that I bought in a moment of confidence and wear more than either of the others. That last one cost $180 and I have worn it perhaps sixty times, which is a better cost-per-wear than most of my tailoring.

The drawstring should be flat cotton tape rather than round cord, since round cord knots into an unopenable nub and stays that way. This is a two-dollar detail that determines whether you will still be wearing the short in three years.