It's like weird Extreme Sports
2. Cave diving
Underwater caves may be gorgeous geological formations full of fantastic fauna nestling in marvelous mineral encrustations that you just can’t catch on a regular scuba dive. But the skills required to navigate these awesome aquariums are such that less than one per cent of the general diving population are qualified. In addition to freezing temperatures and low or no visibility there’s that ticking clock on your air supply. Caves have ceilings and tunnels an eel couldn’t slither through, so waiting until that pressure-gauge needle hits the ‘red’ zone before bailing pretty much guarantees that you won’t see daylight again. Even the American National Speleological Society defines a successful dive as “one you come back from”.