I was given this toy second hand from a friend who's son had outgrown it and it has turned out to be my 9 month old son's favourite bath toy. He's not really interested in any of his other toys (ducks, boats etc), but as soon as he hears this one singing his whole face lights up, a huge grin comes on his face and he squeals in delight.
Unlike the other reviewers I have not had any problems with the singing being too quiet, and can still hear him fine even under water. I agree that the 'arm's aren't really strong enough for him to be able to swim as such but that doesn't bother my son as he loves to watch his arms spin around in the air and he tries to catch them. He even tries to sing along with his catchy tune (and yes, it does get stuck in your head!)
We've had this toy for about 5 months now and it's beem a hit at every bath time, it even stops him crying when he's getting dried off!!