This is a lovely little neoprene wrap, worn by our now 11 month old baby. We previously had the same one in the smaller size also.
When our son is swimming at the hydrotherapy pool for his Waterbabies classes, the room and water is kept incredibly warm, and this wrap isn't necessary (we just use the Splash About Reusable Swim Nappy, also in blue stars, plus Happy Nappy disposables), but if we stray to the public pool this is perfect to keep him that little big warmer.
When he was tiny we had this in the smaller size, and it was indispensible - both because it keeps very young babies warm enough, who tend to chill very easily, but because it also made it easier for us to hold him when in the water. It turns out wet babies are incredibly slippy!
The neoprene is lovely and soft, and the way the entire wrap folds open, so you can simply lay your baby down on top to 'strap him in' to it is fantastic - particularly if you're on your own with the little one. The colours haven't faded with washing, and are much nicer than they appear in this photo.