What's the better thing to wear to the pool? [Question for Girls]?

Okay, so I'm wondering whether or not to wear a t-shirt to the beach/pool/waterpark party thing we have, Anyways. I'm not fat or anything, I don't have a beer gut, But I'm not like skinny or a 6-pack guy either. I have a kinda flat-ish stomach, It doesn't stick out though. So I'm wondering if i wore a shirt would it be a bigger turn off then if i were to not wear one? (By Shirt, i mean those normal t-shirts like grey colored)???