What Should I Wear To At A Water Activities Day?

I am going to a 'waterday' tomorrow with scouts from all over my county which is basically where we all go to a lake nearby and we go canoeing, kayaking, swimming, etc. and its really great fun but im stubbed as what to wear :/ there will be about 100 of us there and its supposed to be warm tomorrow where I live and my boyfriend is going too so i dont want to be too provocative or too subtle. Most girls are wearing bikinis with shorts and a t shirt but i HATE my legs. I have one big yellow bruise on my left leg on my shin and i have lots of grazes on both my knees and I dont want my boyfriend seeing that :/.. WHAT SHOULD I DO?!! Please Help!