Waterproof Digital Cameras

We are planning a trip to Hawaii with some friends this fall. They have been there several times and love to do a lot of water type excursions. They have gone snorkeling and scuba diving. When they have done this they come home with some pretty amazing under water pictures. Most likely they own a waterproof digital cameras to take this with. I think it is pretty amazing that the capabilities of taking pictures under water is pretty phenomenal.