I purchased this diaper for a recent trip to the beach with our almost 9-month old.  She is about 18 lbs and this size was super snug at the waist and around her legs.  I think it was a little too tight around the legs because she ended up getting a rash, but if I bought the next size up it might not have held everything in...  My advice would be to put this on your baby right before you put them in the pool because it's not absorbent enough to hold in urine if the child pees in the car on the way to the pool, etc.  It's possible that my daughter's just a heavy wetter, but that's how it worked for us.  No complaints about this diaper at all.  The snaps on one side make it so easy to get on and off.