We had driven about five minutes from the house, donned wetsuits, masks, and extra-long fins, and fallen into the sea. The reef dropped away immediately, a wall of flourishing coral, covered with bizarre legions of brightly colored, inexplicable creatures and huge goddamn fish. Now, clouds of pulsing jellyfish are all around us, but Rotondi quickly proves they are harmless by flinging one at me.

Even in Sharm, freediving is the balm to Rotondi's problems: "The scion of dah dah dah," as he mocks his Boston pedigree, he has an old water rat inside him; he first tried scuba at 12. Each time he descends, he takes a single breath and then powers straight down, slowly and steadily, 25 feet, 35, 45 feet, dolphin-kicking like Aquaman or Kevin Costner in Waterworld, chased by shafts of light from the noon sun.

In a few minutes Rotondi teaches me the basics—how to duck-dive, how to conserve energy and therefore oxygen and therefore seconds. In moments I descend to depths I would have assumed impossible without scuba gear. I choose a head of coral and shoot past it on the third try. On the fourth attempt I make it to 40 feet—no record, except for me. And then I float back up through a living ocean, utterly calm, passing a school of wide-eyed scuba divers at 30 feet and popping into the air with a grin. I tread water, panting, until I can shout a goofy "Wow!"

"Uh-oh," Rotondi says, heaving another jellyfish my way, "now you're hooked."

He's right. As I drive north that night, the moon lights a fantastic landscape of crumbling ridges and twisting canyons. The brassy casinos and discos of Sharm are forgotten in the cool and quiet of the desert, and when I enter Dahab I realize how easily a place like this can break your heart. The main street is mostly dirt, even if they are filling it in with bricks, slowly. It's closed to cars, most of the time, and regular Bedouin men still pass by, sometimes on their own camels or on frisky Arabian stallions. There are no ATMs, no FedEx boxes, and it's hard to make a phone call, so you don't.

For $300, I sign up for a class at the Dive Zone, Rotondi's last toehold in Dahab. As a non-diver, I'm naturally concerned about safety standards at a bargain-basement dive shop in a fly-by-night town in the Third World run from afar by a Massachusetts swami defaulting on his grocery bills, but I want to see Sinai business Rotondi-style.

The Dive Zone, it turns out, is busy and well run, with a knowledgeable staff of Egyptian and Western dive masters. My two classmates are young backpackers bumming through the Middle East on dollars a day, and the three of us put in a couple of cruel 12-hour classroom days. The Icelander is a burr-headed kid; of the lovely Swede, the less said the better.

Our instructor is a lean, browned South African who has made more than 3,000 dives and seems perfectly credible saying things like "I held my breath for six minutes and thirty-two seconds," or "I dated Miss South Africa for five years." By day we go diving—along the eel garden, where hundreds of the whip-thin creatures sway in the current like seaweed, or eventually into the dangerous and alluring Blue Hole itself, an astounding, deep cenote just offshore that seems to be drilled right through the reef. By night we lounge in the interchangeable seaside restaurants, where the service is criminal, the food insipid, and the setting sublime. The only way to choose among them is to wander up and down listening to their sound tracks, either hippie-residual bursts of Marley and Pink Floyd or the latest European thump.

One night, our class waddles down this aural promenade decked in a hundred pounds of scuba gear, passing dazed divers and red-necked backpackers and Bedouin women amused to see foreigners also veiled in black. We wade out into a bioluminescent sea and float there for a minute, adjusting our buoyancy, watching the glowing lanterns of the waterfront. Then one by one the South African, the Swede, and the Icelander drop down into the black. Just before I slip under the surface, I hear the cry of the muzzein drifting across the water, calling the faithful to one final prayer.

After a few days the three of us get seriously blissed-out. For the Scandinavians, it's the sunburn. For me, it's the impossibility of receiving a phone call. I think of a reason to stay a few more days, and then a few more. I forget my PIN number. I go nine days without donning shoes. At night, I practice holding my breath and contemplate becoming a dive master myself, staying on the beach, getting lean and brown, maybe dating Miss Botswana. I begin to like Dahab, too much.

One night, after a particularly fine dive in the Blue Hole, we dine overlooking the Red Sea, the darkness and the breeze soothing our parched skin. Right before you climb into the turquoise water above the Hole, you pass plaques lining the beach for all the divers killed there over the years, one just three weeks before our arrival. The Red Sea is a particularly dangerous place to dive. It gets so deep so quickly, and inexperienced divers trust inexperienced operators to take them deeper than they should go; it feels thrilling and even spiritual to descend to a hundred feet and feel the ocean still falling away. The Hole seems twice as beautiful in the face of its fatalities, just as Dahab seems precious precisely because it is flawed.

The Icelander isn't as dumb as he looks; he destroys me at chess, and then the Swede leaves, and we sit there, missing her. We stare out over the water. Three boys on camels race up and down the beach, hooting. The moon rises like a pumpkin over Saudi Arabia.

"Man," the Icelander says, as blunt as always. "If you had a chick, this place would be perfect."