beach ball 
noun
A large inflatable ball used for playing games on the beach.You can also write the details on an inflated beach ball and then deflate it to mail or give to the invitee....
- During a party for the kids a year ago, everyone played softball, with a beach ball being used for the ball.
- In the pond where Otis, a Brazilian otter, once thrilled visitors with his spectacular antics, his orange beach ball floated, waiting patiently for Otis to take it for a spin.