When I was there 6 years ago they came in number sizes.
Just note if you have anyone small in your group- They don't have very small adult sizes. I got the smallest women's adult size that I could and it wasn't tight to my skin so I was pretty cold the whole day and it felt gross with sort of a loose wet suit hanging off of me all day and the water was just floating all inside it as I swam. I should have gone back and maybe asked to try a child's, but we were the first dolphin swim of the day and there was no time.