Flotation keyrings. These are tough foams coated in rubbery soft plastic. They are very floaty, and will even float a heavy set of keys. (They are also reminiscent of Lucky Charms Marshmallows) This type of key chain is often given away by Yacht-Brokers. The image in the corner is of the Sonic one being floated in a pool of water. Look at Eggman's one, it is even Egg shaped!