In days of yore, when men were men and cameras took real pictures, one occasionally heard of hockey pucks like the Canon New F1 (for some reason, the New F1 was always described as a "hockey puck") being dunked in seawater, rescued, resuscitated (usually with a soak in fresh water followed by air-drying, after being opened as much as possible to said air) and revived, to go on soldiering for years afterwards. Nothing could stop 'em.
But a modern DSLR? All those delicate electronics? Forget it, right?
Wrong, pixel-breath. Planet5D tells the rather remarkable story of two Canon 5D Mark II's that went swimming and lived to shoot again, in what must have been very alarming inadvertent tests of their weatherproofing. Who'd a thunk they'd survive a dunk? Yet they did.
And if you need to shoot video underwater without taking your 5DII down on purpose, there's always the Liquid Image VideoMask:
Just be sure to be careful where you're looking, because that's being recorded too!
(Thanks to Dirk Rösler of Japan Exposures and Michael Sullivan)