Going to a public pool I will take the swim briefs that I want to wear that day. Colour, design and newness will have influenced my choice, do I wish to show up or blend in on this particular day.
I'll also carry a couple of "old faithful" swim briefs as spares just in case, these are swimsuits that I know I can wear just about anywhere any time.
If I'm in the pool locker room in a state of undress and discover that the waist cord has pull out of one side rather than spending hours trying to re-thread them I'll simply pull on the spare speedos.
In France my car broke down and got towed to a "secret" garage full of broken British cars and camper vans. I was told I was to be taken to a campsite and given 10 minutes to pack. I grabbed tent, sleeping bag, small stove, mess kit, torch, satnav, passport etc but no speedos.
The campsite turned out to be a ***** luxury campsite with an ultra modern aqua centre with 3 pools, one indoors:
https://www.eurocamp.co.uk/campsites...2&gclsrc=3p.ds
Shorts were banned in the aqua centre as everyone wore shorts all the time there so I had to buy slate grey square cuts from the campsite shop.
Always have speedos and spare speedos with you when you are traveling.