As far as I know, no one has ever used a Mac underwater. But taking a camera underwater is relatively common, and the results can be spectacular. Recently, I saw the results of the Monterey Shootout, a contest for amateur photographers who are certified scuba divers. Participants can use film cameras, digital cameras, and videocameras (traditional or digital).
The Monterey Shootout is a race against time, weather conditions, and other photographers. The photographers have 24 hours to walk, wade, swim, or boat to somewhere in California's Monterey Bay and then shoot like crazy. At the end of those 24 hours, participants hand their film, digital files, and movies to the judges. A few hours later, contest officials use PowerBooks and a projector to display the winning images. You can see a sample of those on this page.
The prizes are impressive, ranging from a $150 gift certificate at a local dive shop, to a copy of Adobe Photoshop, to an underwater camera housing that costs thousands of dollars.
You can find a lot more about the contest on its Web site. And if the murky waters of Monterey Bay aren't your ideal destination, check out the Shootou's other location: Fiji. I wonder if my boss will send me to that one...