I had to reorder a smaller size and it's still too big!! I had originally ordered a size 5 for my 5-year old and then had to reorder a size 4 and even that is still too big for his 39 pound frame.  These fit quite large and aren't that great in quality.  They are very thin and flimsy.  The material is nothing like what it should be, it's very thin and loose fitting.  A swim top should be fairly tight.  If I went to a size 3, it would then be too short.  I prefer the Volcom swim shirt I bought at Macy's for just a few dollars more.