When I see a bulge, I try to enjoy it as much as possible by trying to be discreet if necessary. Also I'm careful not to get hard because I grow easily (keep it in your head for the end).
A rather similar situation happened to me. Last summer, I tried surfing with friends (some had already done it but not me). I don't have much balance so I might as well tell you that it wasn't a great success...
Before I started, they told me that the wetsuit could be difficult to put on and take off but not how tight it was! Despite the lack of space, my dick was starting to get fat because of the friction. I'm not talking to you about a discreet semi but about a horse boner, I've rarely been so hard ! And it goes on all along...
I let you imagine the reaction of my friends, between those who laughed and those who were embarrassed. Especially when they told me to cum in the changing rooms when we had finished !
If it's not for my sporting performance, I at least got noticed for something else !
If I have to try surfing again, do you have any advice against erection and/or friction to give me ?