I am a fat 13 year old girl.... What do i wear to the beach?

My friends always invite me to the beach but i always make up a reason to not go. I have succeeded in not having to wear a bathing suit around my friends. I really want to go to the beach this weekend and it has been hard to find something to wear. i have thought about just not going into the water and wearing regular clothes but i want to have fun this time. I am a boy-ish person but all of my friends are very girly. They are all very fit and pretty but im not. So if you have some good advice, please share.