Michael Bennett can remember the moment of truth with absolute clarity — the moment, out in the middle of the Kaiwi Channel on a 12-foot paddleboard, when simply being fit was not enough.

After five hours of flogging the ocean in a race between Moloka'i and O'ahu, Bennett's arms felt like they were about to fall off. His wrists ached as if he had sprained them. He was seasick. His board felt like a writhing alligator.

And the tide was shifting. If Bennett stopped paddling, the currents would push him out to sea.

This is where most people think about quitting. But Bennett, an ultramarathoner whose bucket list includes a climb to the top of Everest and a 135-mile run across Death Valley in the summer, yearns for this point in a race. Something happens here that's greater than endorphins.

"You realize you only have today," he said. "There may not be tomorrow. When you are out there, you realize this is what you have, so make the best of it because you may never be given this chance again. You can always quit and give up but if you don't, you are going to be better for it."

Bennett didn't need a paddleboard race to prove his mettle. The 42-year-old retina surgeon has an athletic resume that includes twice qualifying for the U.S. Olympic swim trials, finishing eight full Ironman triathlons around the world, finishing a 100-kilometer trail race on Tantalus and an attempt last August to complete the Leadville Trail 100, which packs a 100-mile mountain bike race and a 100-mile trail run a week apart.

The Leadville run got the better of him at mile 48. The medical crew pulled him from the event.

"I have size 10 feet and I ended up with size 14 blisters," he said.

Until two months ago when he injured his right knee, Bennett was training for a 100-mile trail run in September in Utah. To complete a distance like that requires intense discipline. Bennett's weekend training included 12-hour runs on trails above Tantalus, Nu'uanu and Manoa. He'd stash food and drink in the trees and consume what he needed between 20-mile loops.

"None of it is hard or the high-intensity stuff where you get injured," he said. "The majority of it is concentrated into building an aerobic base — endurance fitness."

Bennett, a partner in the Retina Institute of Hawai'i, said the solitary effort of an ultramarathon run is an escape from the rigors of eye surgery, vision research and writing grant proposals.

"To be able to decompress at the end of the day is mandatory," he said. "I enjoy the training and being out there doing something physical probably more than I do the racing. I enjoy putting my mind on auto pilot."

But that wasn't enough of a challenge for Bennett, who decided in April to enter the 32-mile QuiksilverEdition Moloka'i to O'ahu Paddleboard Race even though he had never been on a paddleboard. He figured that because he had been competitive swimmer, paddleboarding would be a snap.

The first time he got on a paddleboard, he fell off about 50 times.

"I was just flipping off this thing like I was in a log rolling competition," he said.

During the race, the waves came at Bennett from three different directions, but conditions were at their worst with seven miles to go and the tide sucking him away from Portlock and the final stretch for home.

"That is where you get to know yourself really well," he said. "You have these moments of introspection. You start on that beach in Moloka'i and by the time you hit Portlock, as you are coming to the finish, you are certainly a changed person. You end up pushing your body through things."

It took Bennett another three hours to reach the finish. His time of 8 hours, 25 minutes and 45 seconds placed him near the end of the pack, but not among the 10 people who couldn't complete the race.

"I was asked the other day why do I do this," he said. "It's to see what you can't do. I try to do these things because there is a certain point where you are not going to be successful. You learn more from your failures than your successes."

On Aug. 24, he'll have another chance to flirt with failure. Bennett plans to enter the prestigious Catalina Classic — a 32-mile paddleboard race from Catalina Island to Manhattan Beach, Calif.

Weather conditions are usually good when the race starts at 6 a.m. and can stay that way as paddlers navigate1 one of the busiest shipping channels in the world. But at the five-hour mark, the moment of truth arrives: West winds hammer paddlers broadside with enough force to drive them off course.