I still have one for hang gliding, it works well. However it isn't potted for water service. I have yet to use one of these but what most kitesurfing instructors are using is a VHF walkie-talkie in a bag housing. I don't know if they use it in voice activated mode or if it is just one way for instructions for the student. I would think background noise would be a problem. However when you are on tow background noise generally falls away once you are a distance from the water.
I would think over that suggestion to try towup hang gliding some more. Your first tandem flight is to about 1400 ft., you get to fly on your first flight and the view over Biscayne Bay, the ocean, sharks and dolphins in the shallows and even the Miami skyline is pretty impressive. It only lasts about 15 to 20 minutes but it is memorable.
http://www.miamihanggliding.com/ . You will learn about weaklinks, tow systems and bridles, maintaining tow line tension, avoiding overflying if you pay attention during your tandem session. It would take a lot longer to learn this stuff in a course, if they even offer one these days in boat tow technique. Easy info, no pain and not much risk involved.
If you really want to get big air, hang gliding and paragliding are the way to go. On the land in hang gliding we tow to 2500 to 5000 ft. plus. Hundreds of guys have already been killed and maimed in the development of functional, durable flight and safety systems over the decades. Today, things work well. In 2002 there were NO hang gliding or paragliding fatalities in the USA, in 1974, the early days of hang gliding, 40 died in the USA alone. Being in the early part of the learning curve in a new inertia sport can suck with the injuries and fatalities.