Use a waterproof case, or waterproof video recording device. Attach the suction cups to glass/smooth tiles in the pool, or use the open hooking end with a rope or string. Get creative and you can get any amazing shot you can dream up.
There's something about umbrella's on beaches that i am in love with; ie: jack vettriano's 'the singing buttler' or 'meditation' by sally seago. this, however, has a perfect reflection. must extend my art collection to include.