It's 7:30 p.m., the sun has been down for about an hour, and I'm getting ready to plunge into the inky black water of the Great Barrier Reef. Below me is a group of hungry whitetip reef sharks, ...

I'm breathing faster than I should. In scuba, you want to take long, slow breaths, not quick, staccato ones. But this is my first time diving at night, and when I turn away from the five fellow divers ...