PREPARATIONS WERE SIMPLE. I chose the British Virgin Islands because they looked close to one another on a Web site's cartoon map. The southeast trade winds dictated a southwesterly route: Virgin Gorda, Ginger, Cooper, Peter, and Norman. Ginger Island was uninhabited, so I'd have to camp, but the rest was resort splendor all the way. Twenty miles of fun-filled Caribbean waters, if you could put out of your mind what the St. John–based kayak guide told me:

"Oh. Ginger, huh?" Arawak Expeditions owner Arthur Jones said when he heard my plan. "I don't know—it's pretty sharky. I remember hearing about someone else who tried that off St. John a while back, and she had to stop halfway through because of a shark. It just started following her and getting closer and closer. But I don't know. Maybe that was just a rumor."

Suddenly thinking about that old bear joke—the one about not having to outrun the bear, just the guy next to you—I invited my friend Hopper (a.k.a. George McDonough), a 35-year-old landscape architect I'd met at the Y, to come along. A former Division I swimmer at the University of Rhode Island, he was about three months behind me as far as getting back in shape was concerned—in other words, a little bit slower.

"Sure," he answered. "Where?"

Hopper actually proved useful as more than just shark fodder. We wanted to be self-sufficient and tow everything we needed. I had the bright idea of using a kid's blow-up raft; Hopper had the even brighter idea of a surfboard: low-profile, able to hold a lot of weight, and with tail fins to keep it in line. Hopper was seeming more and more like a good choice. Not only did he come up with a name for our adventure—SwimTrek BVI!—but he also turned out to be an experienced open-water swimmer, having raced at distances up to eight miles. It was Hopper who suggested we bring duct tape and epoxy for board repair, a VHF radio, a Swiss Army knife, a chart, a couple of pairs of Crocs, and the flag we'd fly above our board to warn away boaters. I came up with resortwear and toothbrushes. In my defense, I also got some racing wetsuits that would protect us from Linuche unguiculata, the stinging, itching thimble jellyfish that are everywhere you want to be in the Caribbean in the warmer months. But the airline lost that bag on the way down.

About the only thing Hopper wasn't prepared for was hostile locals. Our first night in the islands, at a bar near our Tortola hostel, he was laying it on thick with Simon, the bartender, perhaps hoping we'd get a few free drinks, when this good-looking Australian woman overheard us talking about our swim.

"Really?" she joined in, pleasantly enough at first. "That doesn't sound very hard—only a few miles between them."

"I know," Hopper answered. "Although everybody else we've told hasn't believed us."

"It's just 20 miles in a few days," I added. "Anybody could do it."

I was about to get up and stand closer when her entire expression changed. It reminded me of a look my high school water-polo co-captain would get before kicking me in the balls.

"You're liars," she spat out, but she wasn't done. "You're not swimming anywhere. Nobody'd be that stupid. Do you know anything about the currents between the islands? You can't swim against them. I've dived in there enough to know. You're a bunch of wankers."

"Oh, no," I replied, raising my eyebrows. "We're definitely doing it."

"Fuckers."