I haven't worn this in the water yet, but I love it!  I'm 5'1" and 150lbs. I normally wear a large or XL, or 12/14.  I ordered the 4xl and it is just a tad big on top.  I can wear it, but MIGHT have been able to wear the 3xl. But I really hate things to be too tight and show back fat, so I will keep this size.  It really is adorable!