Suspended eighty feet underwater, I have a few seconds to take in my surroundings. My heartbeat—the only sound I can hear—marks the time. My lungs are now less than a third the volume they were twenty seconds ago. Abdominal muscles clenched, I restrain the spasms of my diaphragm, willing myself to ignore the steady toxic accumulation of carbon dioxide in my body. Mere minutes from drowning, I am relaxed. The crack in which I am suspended is visible from the surface. Minutes earlier, as I floated on the surface deliberately slowing my breathing in anticipation of the dive, I studied the contour of this particularly severe crack in the reef, noting its abyssal blue hue atypical of most sand chutes. » read more «