Floating keychains are common, but this is the first time we have seen something like the Waterbuoy: you chain it to whatever valuable object and, if it falls into the water, the contact will fire up a gas valve that will instantly fill a balloon capable of lifting 1kg. The water will also activate a high-intensity LED so you can see it at night. Warning note: never store a keychain in your swimming trunks’ pocket. Or else. [Besportier]