Big wave surfer Shane Dorian almost drowned in 2010. After wiping out on a huge wave, he was pushed down 25 feet to the ocean floor, where he was held as two more huge waves rolled over him. The experience led him to conceive of the world's first inflatable wetsuit.
The V1 is like a normal wetsuit, but it's got a cord attached to it. Like pulling the cord on a parachute, you simply give it a tug if you're in trouble under the water. A pouch on the upper back instantly inflates and sends you rocketing up to the surface of the water. It's easily refillable, once used; simply pop in a new CO2 cartridge and you're good to go.
Unfortunately, the V1 isn't commercially available at the moment, but hopefully it will be in the near future for not too high a price.