A volleyball. Yes, in order to play volleyball, a volleyball is typically needed. Don't quote us on that, though.

A net. It doesn't have to be on sand, but that would probably help.

Sunscreen. When you're out there dominating the sand courts for over several hours a day, your skin will probably start to burn. And then peel. Melanoma is not your friend.

Sand. You know, the reason why they call it "sand" volleyball, as opposed to just "volleyball."

Don't be rude. Share the space. (Source)