[Torchwatch]

Wherever you go take a choice of swimwear.
Short shorts that you are comfortable in.
Squarecuts.
2-3" swim briefs.
1-2" swim bikinis
and maybe even a swim thong.

If you find yourself alone wear whatever you like.
If you find there is a crowd there already conform but wear slightly less than everyone else.
If you just have speedos and the crowd appear hostile it may ruin your day, by having a choice of swimwear you can adapt to the mood of the crowd.
If you go in the water and get you swimwear wet you can always slip into something briefer when you come back out.
There may be other guys around wearing long shorts that would prefer to wear something briefer but nothing will happen until someone sets an example.
At your local pools look for the lane swimming sessions, especially before or after the booked club swim sessions. This is when more serious swimmers wanting to wear less that baggy board shorts will be around.