Mobile phones
While I'm at it how about mobile phones? Drop anything electronic overboard and that's the end of it - unless it is waterproof and floats, this pack has a revolutionary seal which locks water out, and air in. Whilst the tough but soft case allows you to hear, speak, or press buttons through them, as normal.
Cameras
Finally another vulnerable item in danger of dropping overboard is your expensive camera. If your camera is not designed to be used underwater and you are desperate to take an underwater shot then you could try this product. It allows you to press the shutter through the bag. Probably cheaper than investing in the real thing if you don't need the facility all the time.
If you are seriously interested in underwater photography then one issue you will need to consider is the question of increasing pressure as you go deeper. With a rigid container any slight leak will cause the water to gush in, not in a steady dribble but the deeper you go the faster the flow. One solution to this is to make the housing flexible, so that it simply contracts. Another advantage is that the camera can be operated through the plastic transparent covering. Flexible coverings still need to have a pressure resistant sealing system.
Visit www.ifsogo.com for more information.