Alien Nation Kona, Hawaii

I'll admit it: As I stood on the swim step staring down at the bottomless black open ocean off Kona, I had the same tingle of fear ripple under my skin that I'd long relegated to the dark closets of my 3-year-old imagination. It seemed silly. Irrational. I've done hundreds of night dives. But there it was: fear. I began an inner dialogue with myself, wondering what kind of abyssal alien warriors would rise up. More than that, I wondered if I'd get bumped by something big in the dark. I admonished myself for these anxious thoughts. Even as I giant-strided – taking one last look at the lights of Kailua-Kona on the horizon – and hit the water in an explosion of bubbles and silence all at once, I grappled with this strange feeling. Immediately the civilized, terrestrial world bowed out, leaving only the deep, noiseless badlads of the open ocean.

There were three of us, and I was the last one in. I tethered myself to the weighted-down line feeling very much like bait on a hook as we drifted in the pitch-black ocean alongside the boat from Jack's Diving Locker. Our lights seemed puny – small bits of illumination on an immense black field, barely holding the dark edge at bay. I could feel the vastness of the Pacific Ocean and the odd sensation of vertigo that comes in a dimensionless world void of reference. It didn't matter whether the bottom was 100 or 10,000 feet below me; I was in a foreign place, hanging from a line at 60 feet, and if I faced east I was farther from land than I'd be anywhere else on earth. I can think of no better way to humble oneself than to immerse a trifling ego in such an infinite place. I was happy for these thoughts, though, because I could feel the fear ebbing, giving way to curiosity about our place in the world. And in my lights the small nocturnal travelers began making appearances.

We were all told during the briefing to focus on the "small": the minute specks that would inevitably float past our lights in jerks and jolts and wild wiggles of abandon. These iotas of life, miniscule and hard to distinguish, were all living things – life forms that seem built of water and framed with captured touches of light. Soon, the fear had gone. In its place was awe, risen from the dark chasm beneath me. I saw larval stages of common marine life that, on close inspection, defied logic: transparent beings, phytoplankton, pelagic tunicates, jellies seemingly built of rainbows, and siphonophores, whose internal organs were the only features to betray their otherwise invisible bodies.

None of us wanted to surface.

But we'd only really know, or be able to define, what we'd seen when we got back to the boat to view the video and still photos. Blown up twice life-size, these little spirits of the deep looked like extraterrestrials: bug-eyeed, scythe-armed, ghoulish and frilly invaders from deep, deep space. We stared with speechless disbelief.

On the return to the harbor, as the lights of Kona loomed closer, I knew I'd discovered another reason to take to the sunless sea.