I saw this idea on Crafty Vegan's blog last week, it's a pillowcase bag from Martha Stewart. I used a vintage case from my Grandma. It was very simple and I think it'll be just right for the beach. It's the kind of bag you can get dirty and toss in the wash. The pattern was very easy to follow and I made only 2 changes - I sewed down both diagonals (4 diagonals total) so that it wouldn't flop on the inside (hope that makes sense) and I added a snap. Can't wait to use it!