We're not big boaters around here—we can kinda swim, but don't know how to breathe correctly—but the key buoy would still be super useful for us. Why? Because even though we don't go in boats, where this keychain has the most benefit by keeping your key on the surface of the water, we still manage to drop our keys in the pool, the tub, and the toilet more often than you'd imagine.
When unsubmerged, the key buoy looks like a normal fob, but once it hits water it pops up and lifts your keys to safety. That is, unless you've got some special keys—like if you were a janitor or you had the key to the city.