The key (bracelet) to swimming in France

I knew when returning to the Alps that there would be a last minute chance for a swim. While there were pools in all the places we'd stayed - they hadn't opened for Summer yet. So I'd been out of luck.

I discovered last time we were here that there are systems to follow at the pools in France. It's not like at home where you wander in, pay your money, and get into the pool at your leisure. What would I be getting myself in to here?