The Beach Ball is an item that can be found in Water Chests located anywhere. When the Beach Ball is consumed, it creates a moving item that the player can knock around by touching it. The item will be unaffected if touched by a mob. When the Ball stops moving it will drop as the Beach Ball item which can be collected and used again. It is a useless novelty item.
Terraria 1.2 - How to play football (kinda)