Seemed like a good idea, so I tested this on my new Pentax Optio WP 10. You can get these key floats at just about any bait and tackle shop or Wal-Mart. I happened to have a Boater's World float (white) and one from Wal-Mart (orange). Turned out that the W-M float was slightly longer and fatter than the BW float, so you might expect that it would provide better flotation for the camera-and it did. Here are a few pics for comparison using the Pentax. I always use a neck lanyard and carry the camera in the breast pocket of my T-shirt or fishing shirt, so that is what you see floating in the bucket.
Here is a closer view of the float. You can see that about 80% of the BW float is submerged with this camera.
Here is the same setup with the orange W-M key float and attached lanyard.
And, for comparison, here is a closeup of the W-M float and camera. You can see that only about half of this float is underwater, so obviously this one will give you the best flotation for your camera. As another advantage, the W-M float has the safety orange color, so it might be a bit more visible at the surface should it get dropped overboard.
Digicams, neck lanyards, and key floats-don't leave home without them! Remember--if no pics, it nevah hoppened.
