ACCESSIBLE ONLY BY BOAT, Pilottown, Louisiana, has been used by river pilots for more than a century as a base to meet ships heading up or down the Mississippi. The rodents come beagle-size, and the mosquitoes, as locals say, are big enough to stand on two legs and stare a turkey in the eye. "It ain't the Four Seasons," says Clasen.

But since it's fewer than two miles from the mouth of the Mississippi, it's the best place to start a trip to the rigs, which is why Clasen still keeps the island's last privately owned cabin. Thirty-year-old Brian Head has joined Clasen, Kirkconnell, and me on this humid August evening, and under the harsh glare of exposed lightbulbs, they are making a "flasher," a cluster of reflective objects meant to attract fish.

We leave at six in the morning. Clasen stops in at Pilottown's HQ to check the status of Hurricane Gustav, which has already hammered Haiti. "The hurricane is heading right towards us," he says while we load the boat. His tone carries more exasperation than fear, as if he were speaking about an obnoxious uncle that occasionally visits. "We'll dive hard today and tomorrow," he says.

The 3,800-plus production platforms that pincushion the Gulf of Mexico face a constant threat from hurricanes. In 2005, the most damaging season in the Gulf oil fields, Katrina and Rita destroyed 108 structures and caused more than 7.1 million gallons of oil to spill across southeast Louisiana. Still, Clasen, like many Gulf residents, accepts this dance of disaster as routine.

When we stop at our first platform, 20 or so miles offshore, I ask Clasen if he knows its name.

"Yup," he replies tersely, ending that line of questioning. These platforms stand hundreds of feet above the water, are visible from miles away, and are owned by the likes of Shell and Exxon, but still Clasen treats them as closely guarded secrets. "I don't let my friends take GPS's on the boat," he says.

After catching a few bonito (a blue, leopard-spotted relative of the tuna) for chum with a rod and reel, we continue deeper into the Gulf. Anything that floats—plastic buckets, driftwood, trash—can create a thriving if temporary ecosystem. We pass a few small patches of sargassum, open-ocean seaweed that can form giant floral rafts. Kirkconnell and Head clamor into the water carrying a camera and speargun, respectively, swim right up to a dorado as if asking for directions, and bury a shaft behind its gills.Dorados are brilliant in coloring if not intellect; because of their rich sunshine hue, they were named after the Spanish word for "golden" and are known for a Technicolor display of green, blue, and yellow as they expire. It's morbidly stunning, in a smoggy Los Angeles sunset kind of way. They're even better known as damn good eating, and as Head hauls the first catch of the day into the boat, Kirkconnell says, "Well, we have dinner."

Thanks to the heavy flow of nutrients flushed into the Gulf by the Mississippi, Louisiana waters are at the epicenter of what's called the Fertile Crescent, an area of consistent and exceptional productivity. Second only to Alaska, Louisiana brings in about 12 percent of the country's annual catch and $271 million a year in revenue. Certain species, like the near-shore red snapper, suffer from overfishing, in part because they are victims of bycatch, caught in shrimp nets. As the dorado, a healthy fish stock, sits on ice in the boat, Kirkconnell is quick to point out that spearfishing is the most sustainable form of fishing, because every animal is taken with intent, eliminating bycatch.

As we approach a cluster of rigs, an explosion of mist appears above the water.

"Is that a sperm whale?" asks Kirkconnell, squinting his tight almond-sliver eyes. He instantly recognizes the giant by the shape of its spout and grabs his mask and camera, preparing to film the world's largest toothy whale. "I hope that's not a sperm whale."

"Why, what do sperm whales eat?" asks Head.

"You mean besides giant squid?" I reply, recalling that these leviathans inspired the monster Moby-Dick. The whale exhaled again, spout hanging heavily in the air like my question.

"Yup, that's a sperm whale," says Kirkconnell as he rolls into the water.