You could give everyone a piece of fabric or a sheet and have a costume contest. Give everyone a paper bag with safety pins, glue, buttons or assorted junk.

So one of my friends is going away to Palestine for a few months & I'm gonna throw him a surprise party at the pool. I need ideas for activites I just don't want it to be boring ya know? Theres gonna be about 20 people so what should we do ? And theres also a indoor balcony type thing ( but obvi its not really a balcony) where theres tables for food and stuff and the party is gonna be at night.. any ideas? Thanks :)