Keep your phone dry!
Dry Case keeps your phone or camera dry to 100 feet by using vacuum sealed technology. Has facilities for headphones and mike jack and is crystal clear for taking photos. Comes with a bulb to pump out all the air and a buoyant armband as well to keep it afloat should you turn it loose while in the water. Dry Case has waterproof headphones and mike and several styles of waterproof and floating bags and backpacks. Some with strong suction cups on them to attach to you ski or surf board. Impressive stuff for extreme sports types. Or normal people too.
As a rower/sculler on the Thames I can see the value of both the phone cases and the backpacks, not just for splashes, but the occasional capsize!