If I ever have a pool I'm totally going to get these! The Ocean Art Light-up Jellies from Swim Ways are eerily life-sized jellyfish decorations for swimming pools. Each light-up jellyfish has LEDs inside and glow as they float across the pool
Helium filled balloons tied to weights in pool. If you want to create the illusion of floating balloons use fishing line which is virtually invisible. (IDEA- Could also ADD some glow sticks so that the balloons GLOW over the Pool at NIGHT!