What to wear on a boat trip with boyfriend's parents?

Double check with your boyfriend because a boat trip doesn't automatically mean you are supposed to wear a swimsuit. It depends on the nature of the trip. Most people wear cool comfortable laid back clothing but not a swimsuit. If it's a small boat out on a lake and you are likely to go swimming, a bikini should be fine as long as it's got full coverage on your butt. If it's more of a cruise, you should wear something like a sheer top with a tank under it and long lightweight flowy pants and flip flops.

Pants like this...

You're 24, I think it's safe to assume you're an adult... wear a bikini. Or least short shorts a t shirt over it.

wear a bikini ur old enuf lol :-)