Boating???????????

I'm going boating this summer. We will be out there pretty much all day for like 2 or 3 days. When we first get out there, it might be a little chilly, but once it warms up it will really warm up. I won't be getting wet or anything. I want to wear my bathing suit, but is that ok or too inappropriate? I don't want to wear it when we first get there, it'll be too cold. So, I don't know what to do. Please help! Any ideas? THANKS!