A water ball or water walking ball is a large inflatable sphere that allows a person inside it to walk across the surface of a body of water. The giant ball is usually two metres in diameter and has an airtight zipper(SZIP Easyproof) with entrance to allow for easy entry and exit. The water walking ball is similar to the zorb but it has only one layer and is designed for water travel rather than down-hill rolling. In the United Kingdom, the balls have been used at swimming pools, marinas and lakes in an effort to keep children fit. Here is some pictures for reference.