It's an American thing. On a FB group I've seen people getting hundreds of these things custom printed with a band logo which is so incomprehensible to me because 1. It must have cost them, 2. Not everyone likes the same band as you, and 3. WHY
As the owner of a young child, bath toys that are squeezy with a hole in them are a breeding ground for black mould as the water can't escape once it's inside. So these things are no good for young kids even! I guess my son would be happy to find one and I'd let him play with it but not in water.
On NCL they have grab machines with ducks in various designs so maybe that's where the idea originated- people won the ducks and then rehid them around the ship?
My mum crochets (with real wool) small toys and leaves them in local parks for children, I know people paint rocks and leave them to be found and rehidden. Much more environmentally friendly versions of this game!