Glad I am not into swimming as no hiding mine in any way, shape or form!
A wet suit fine if your a surfer or a wanna be one but even then going to have some interesting bulges on the chest. My old fall back of a football shirt (soccer for those whose football involves an ovoid ball) doesn't work as it will just get all transparent when wet, although might prompt an impromptu wet shirt competition! That said on the beach I normally keep my top half covered anyway!
I guess if your trans and out then its going to be a little easier! Just other things to try and hide instead!
Megan