Fancy playing cards in the pool, or just need somewhere to rest your drink? You can make a cheap floating tabletop from a styrofoam pool noodle and a cutting board.
All you need to do is measure and cut the pool noodle to match all four sides of the cutting board and then cut slats in those pieces and slide them onto the edges of the cutting board. If you size the slats correctly, you won't need glue. Your only real limitation is the size of the board.