WHEN YOU COME TO THE ISLAND OF HAWAII, plan on skipping happy hour. Watching the sun set with your feet up, umbrella drink in hand, may be the way to end your day on Maui, but not here. The Big Island, home to a host of geologic superlatives—tallest mountain on earth (Mauna Kea, 33,476 feet when measured from the ocean floor), largest active volcano (Mauna Loa), one of the most active volcanoes on the planet (Kilauea)—as well as to Pele, temperamental goddess of fire, begs to be taken more seriously than your standard-issue tropical isle. Who cares about sipping mai tais when you can watch manta rays undulate in the deep, witness the fiery red trickle of lava into the Pacific, or see a universe of stars at 12,000 feet? The Big Island has awesome nightlife like no other.

Ray Ballet
DIVE-HEADS THE WORLD OVER flock to Hawaii to see manta rays beneath the waves by night. Being underwater after dark is eerie even on a shallow protected reef. But here, just off Kailua-Kona, on the island's west coast, as I slowly descend with my fellow night owls, I try to forget I'm swimming along the slope of a volcano in the middle of the Pacific. Hawaii calls itself the most isolated archipelago on the planet; it's hard to get farther away from the world's continents. At 35 feet we reach the rock-and-coral-strewn bottom.

We form a loose circle, switch on our dive lights, and angle them up toward the surface like we're prepping for a Hollywood premiere. Staring up at the bright spot where the beams intersect, we wait for the storm of tiny shrimplike organisms that are attracted by the light. Minutes after the water turns snowy with plankton, the mantas fly in from the depths. It's impossible not to imagine them as spacecraft, with their aerodynamic lines and tipped wings. Their rectangular mouths open so wide you can see clear inside their bodies. They cruise slowly over our heads into the middle of their meal, performing elegant backflips. There's never any guarantee that these huge, harmless creatures will show up. But tonight there are easily a dozen, some with 12-foot wingspans. I feel something slither over my hand—a green moray eel on the hunt. A few feet away, he gobbles a butterfly fish whole.