When Warren and Julie Lavender surfaced from their first-ever certified scuba dive on the day after Christmas, they pulled off their masks, looked at each other and said, “That sucked.”

Then Warren threw up.

The dive had sucked because the water was choppy on the surface and the current was hellaciously strong at the bottom and the fish were all hiding in crevices for some reason. The Lavenders happily climbed into the dive boat for the half-hour trip back to the beach, where glorious Alka-Seltzer awaited.

On the way Julie noticed something weird in the water. “Somebody’s wallet,” she said, pointing at it. Then came a chair. Then a coconut tree.

Then Warren noticed something worse--a horrified look on the captain’s face. He spun around to see that the beach wasn’t there anymore. “That’s when we knew something was very, very wrong,” Warren remembers. “That beach had to be 150 meters wide, and it was just ... gone.” So were the docks. Waves were crashing straight into the hotels, some of which caved in like sandcastles.

The Lavenders had unknowingly scuba-dived through a tsunami, which was now hammering their vacation spot, the resort town of Beruwala on the western coast of Sri Lanka, gobbling up homes and boats and people, pulling them into the Indian Ocean and then flinging them back at the town again and again, killing hundreds.

Suddenly, it all made sense to the novice divers, the way they’d had to fight the torrential current at the bottom. “It was like a hurricane underwater,” is how Warren describes it. Twenty meters below the surface, his mask was ripped off. It was all they could do to hold on to coral to avoid being sucked away. “We were hanging parallel to the ocean floor,” Julie says. Warren is 6'4", 280, but Julie is only 5'3". “I was terrified Julie would lose her grip and be swept away forever,” he recalls. “I remember thinking, Gee, I could really learn to hate this sport.”

They eventually made it to the guide rope and climbed to the sunny surface, where “we just thought it was the end of a perfectly normal dive,” Warren says. How could they have known that they’d survived a tsunami that had been moving at up to 500 mph on its way to mauling the coastlines of Indonesia, Malaysia, Thailand, India, Sri Lanka and Somalia, moving entire islands and killing more than 140,000 people in one of the worst natural disasters of our time?

As the boat neared the dive center, Warren says, “everything that the tidal wave had wrecked going ashore was now in the wave coming back at us. The dive instructor told the captain to turn the boat and outrun it, but I said, ‘Screw that! Get us on shore!’ Because with all the debris flying around in the water, I didn’t think we’d survive.”

Somehow the baby-faced captain steered the boat through the whirling chaos. He saw a house balcony that had been ripped away and decided to use it as a makeshift dock. Turned out it was the balcony from the dive instructor’s guest house. She watched, stunned, as the house collapsed, her new Sea-Doo lit out to sea and footlong angel fish flopped on the lawn.

The Lavenders jumped from the boat to the balcony, then ran in bare feet over smashed glass and brick for higher ground. When they hit the street, the couple saw two policemen running toward them, followed by hundreds of wild-eyed locals. Another wave was coming. The Lavenders ducked into a sturdy three-story concrete building and made it to the top floor as the water rearranged the lobby.

Later, they tried to walk back to their hotel but couldn’t find it. Half a kilometer from the shore they passed boats marooned on sidewalks. The Lavenders spent the night on the cement floor of a hilltop home that the owner had opened to the stranded. The next day Warren found the now unemployed dive boat captain wandering the streets, picked the guy up, hugged him and gushed, “You saved our lives!” Then he handed him every rupee in his pocket.

Two days after the tsunami the Lavenders paid a man triple the usual rate to drive them to the capital city of Colombo for their flight back to Kuwait City, where the Canadian couple are schoolteachers. As they drove, only emergency and relief vehicles passed them going the other way. The driver wept.

“It seemed so unfair that we could simply buy our way out of a situation,” Warren e-mailed to friends later, “and so many others have no choice but to stay.”

Looking back, they realize how preposterously lucky they were to just that week have taken up a sport that wound up saving their lives. “If we hadn’t been diving,” says Julie, “we’d have been lying on that beach.”

“Who would’ve thought,” concludes Warren, “that we were in the safest place of all? Underwater.”

• If you have a comment for Rick Reilly, send it to reilly@siletters.com

The Lavenders had unknowingly scuba-dived through a tsunami, which was now hammering their vacation spot.