I go to the beach at 20 years old, and at an older age I always walk in a very open swimsuit. And at 90, if I can get to him, I’ll go open too.
Because on the beach it is accepted to sunbath. What's the point of burning in the closed? It will dry for a long time. Have you tried lying in a wet swimsuit? Cold and ugly.
But in the swimming pool closed swimsuit is the best place. Nothing slips, you can jump from the tower without risking to be without a piece of clothes.