Well folks I found a NEW "toy" to use in pool sessions called the Underwater Sonic Search Pool Game from Discovery Kids store. Click here for website
So far this game looks to be fun. The only draw back is that it is only rated to roughly 6 feet. You get 60 seconds to locate the clear/blue ball by sound, which speeds up with sonic-style tones as the 60 seconds expires. Upon expiration it goes into alert mode and has a 5-10 second siren that repeats for 1 second every 10 seconds.
This is a great educational tool for demonstrating how well sounds travel in water while conducting pool sessions. And for roughly $10 how can you go wrong! Runs on 3 watch batteries.