If you're heading to an amusement park this spring break or summer, this is a great idea to take along. Pick up a Waterproof Bag Case for your Cell Phone for as low as $3.00. Shipping is free. Your final price will depend on which color you buy.
The way I look at it, even if you only use it once, you get your money out of it. Think of the water rides where you need to protect your phone.