THIS CARIBBEAN SWIMMING was really paying off as far as my Olympic dreams were concerned. My shark phobia had me concentrating like never before on making my stroke smoother, and soon I was sliding through the water like a slippery, unappetizing eel.

Day three was a short two-mile but deep-water swim from Ginger to the Cooper Island Beach Club. Practicing good stroke mechanics and head positioning, I would stare straight down, and what I saw wasn't pretty; it was gorgeous, an endless expanse of dreamy blue water that made me think of exploring deep space. I knew I was looking at least as far as 40, maybe 50, feet deep, but the milky blueness was so uniform in this 120-foot water, I couldn't see anything. No bottom, no fish, no nothing, except for an occasional terrifying strand of seaweed darting into view that never failed to make me jump.

Slowly, though, we were developing a certain rhythm—and not just in the water.

What I saw wasn't pretty—it was gorgeous, an endless expanse of dreamy blue water that made me think of exploring deep space.

"I've figured out the ebb and flow of this trip," Hopper said the next morning while I fried up a batch of holes-in-the-wall in our little kitchenette at the down-to-earth resort. He was looking and sounding a little stressed. I was feeling the same. "The tension builds as the swim approaches," he went on. "You're wondering about the variables, the current, the wind, boats, et cetera, and then you're a little bit freaked out when you first shove off. Things start to mellow as your arms loosen up. You're under way. Life is good. Then you arrive and you're all elated. You have a beer, sleep, go over the swim, and then it's just . . . a slow . . . build . . . toward . . . that . . . pre-swim tension."

The best part of swim-trekking was that, unlike 99 percent of the swimmers in the world, we actually arrived somewhere at the end of our workouts and talked to real people. As five-time Olympic gold medalist Gary Hall Jr. puts it, "It's bad enough talking to the stripe at the bottom of the pool. It's even worse when it starts talking back."

On Salt Island, a brief stopover between Cooper and Peter islands on the grueling fourth day of our voyage, we came ashore to find a skeletal elderly man wandering outside the ramshackle cinder-block huts that clutter the shoreline, looking somewhat befuddled in his slightly askew construction helmet. His name was Henry Leonard, he said, and he lived there all by himself. There used to be families scattered all over the one-and-a-half-square-mile island, he explained, collecting salt in the inland ponds. Now it was just him, the rustling palms, and the salt, which stretched behind his shack in a long, uninterrupted sheet of gray. We talked for a few more minutes, but then we too had to shove off.

The six-mile Cooper-to-Peter leg was our longest by far, almost the equivalent in effort of running a marathon. And here it was already 10 a.m., and we still had four miles to go. Hopper and I swam off without Paolo and Derik, but after half an hour and no safety boat, Hopper tapped me on the shoulder. "What do you want to do?" he asked. "Turn back? Wait here?" Surely they'd show up any minute.

Mere seconds later, I was staring again into that never-ending nothingness, screaming to myself, Turn back! This is how it's gonna end! But I kept swimming. After about an hour and no bites to our soft underbellies, I noticed that I was no longer jumping like a frightened surface minnow at every perceived attack. I even started hoping that Paolo and Derik wouldn't show up. I was feeling like part of the ocean, as if I actually belonged in it instead of being a temporary, wary visitor. The wind, now stronger, pushed us down the ever-towering swells. I was Aquaman, Johnny Weissmuller, and a dolphin rolled into one!

I was so happy that I didn't even mind the harbor attendant yelling that we couldn't swim near the boats at the Peter Island Resort dock. When we explained to him that we were a boat, he just waved exasperatedly toward a ladder near a sybaritic 50-foot cruiser.

The worst swim was over, and the most dangerous part of our adventure would turn out to be the safety boat, which in fact sank to the bottom of the ocean as Paolo and I scrambled to salvage his gear a day later. But for now, what'd we care? High on endorphins, we zipped around Peter Island's luxurious digs, playing on Hobie Cats, downing more rum, and getting massaged on a hilltop overlooking nearly all the Virgin Islands. And we were just one day away from the ultimate spring-break party.