Glow sticks in the pool, great for night swimming! Not sure this would be the best idea for a big in ground pool (would probably take a couple hundred sticks), but would definitely be cool in a kid pool or an above ground pool!
I'm a huge fan of swimming pools I used to dream about them. I wish I could own a house with an indoor pool. I love outdoor pools too, but I don't want to be greedy:) Amazing Swimming Pools That Can Beautify Your Outdoor Space.