I hovered in the murky light and checked the screen of my dive computer on my wrist. The chrome dials and ebony numbers shimmered, wiggling like a school of fish. “60m” was blinking excitedly, almost to the rhythm of my air tanks clinking in discordant harmony. I heard the rasp of my regulator as I inhaled, feeling the cold air rush into my chest – although it wasn't as cold as the water. My body shivered; I felt my microscopic cells jog on the spot in an attempt to warm my freezing nerves.

Brightly colored coral glittered among the craggy surfaces of the rock wall. Tiny fish zipped through holes. I reached out to touch a soft pink sponge, and stared as it paled to lily white in fright.

I looked up and saw blue, looked down and saw darkness – but suddenly it all blurred together. I couldn't see anything but a deep, dizzying azure. I felt myself turn upside down like a turtle on its back.

Somewhere under all of my neoprene wrapping, a laugh was brewing. I could feel it bubbling, eager to rise up and out of my gut. I twisted and wriggled with its upward ascent. The sound was harsh as it escaped into the silent void – a raspy euphoria that caused hundreds of bubbles to sprint for heaven.

I felt weightless, and I allowed the surge to rock me gently as I watched a large fish with bulbous eyes and speckled lips. I tried to follow as he sauntered on his way, but found that my legs were numb. It didn't matter; I felt wonderful. I was encased in my own bubble of air, observing a rosy-cheeked jellyfish dance the jive, its many legs sashaying. A dozen rays flew elegantly past in combat formation, and I was thrown back in time to a military air show I had witnessed as a child.

An incessant beeping ­splintered my concentration. I examined my dive watch in confusion. I couldn't read the flashing symbols; my brain was as spongy as the coral alongside me. Yanking at the thick strap, I dislodged it and sent it spiraling into the gloomy abyss at my feet.

I felt slivers of water slip into my suit and leopard-crawl across my skin. I laughed again, opening my mouth so wide that I tasted salty wetness. I wondered if I was breathing water and not air. My hands fumbled as I unhooked my reserve tanks and slipped off my mask, the thin plastic pulling my hair in despair. Finally, I extracted the regulator from my clenched jaw and, smiling, I inhaled.