Fitting for a sport in its infancy, a manchild prevailed at the Sunset Beach Pro stand-up paddle surfing contest yesterday.

Seventeen-year-old Kai Lenny of Maui performed beyond his years to win the contest in difficult conditions at Sunset Beach.

"I was just honored to get in the contest and compete against the best stand-up paddlers in the world," said Lenny, who is a junior in a home-school program. "I can't believe I won."

The contest was the first event on the inaugural Stand Up World Tour, and it drew more than 70 elite wave-riders from around the world.

The final day was completed in wave-face heights of 10 to 20 feet at Sunset Beach. Strong onshore winds made it difficult for the competitors to find quality waves.

Lenny, despite his inexperience at Sunset Beach, said he felt at home in the tricky conditions. The two days of this contest were his first sessions at Sunset Beach.

"Luckily on Maui, I surfed some outer reef breaks that are similar to this wave," he said. "Actually, this would be like the best day on Maui."

In the four-man final, Lenny dominated the 45-minute heat.

His best wave received a score of 8.6 (out of 10), and he backed it up with a second wave of 7.2. His two-wave total of 15.8 was enough to win the $3,000 first-place check.

"We're pretty shocked," said Martin Lenny, Kai's father. "He hasn't proved himself on a world stage like this, so we were happy he got as far as the final. We weren't expecting this."

At the same time, Lenny is considered a rising waterman on Maui.

He is already a full-time member of the Professional Windsurfing Association. He was the No. 19-ranked windsurfer in the world last year, and was named the tour's Rookie of the Year.

He is also a skilled tow-in surfer, and recently rode giant waves at Maui's treacherous "Jaws" spot with expert watermen Laird Hamilton and Dave Kalama.

"Windsurfing is still my focus right now," Lenny said. "I'm still trying to do that tour and win events there."

Now he has to consider competing on the inaugural Stand Up World Tour as well. As the winner of the first event, Lenny is the No. 1-ranked stand-up paddle surfer in the world right now.

"I'm all game now," he said. "I want to do this (tour), too, as long as it can fit in my schedule."

The Sunset Beach event was the first of four scheduled contests on the 2010 tour. Subsequent events are scheduled for France in May, Tahiti in June, and Ocean Beach, Calif., in October.

Kekoa Uemura of Honolulu placed second yesterday. He is a professional longboard surfer, but said he will also consider competing at all the events on the Stand Up World Tour.

"Hopefully my sponsors can dig deep and help me out," said Uemura, 27.

He's also going to need a new board. Uemura's board snapped in half after a scary wipeout in the closing minutes of the final heat.

"The big waves were getting the biggest points, so I was just waiting for one," he said. "I saw that one wedge up and so I paddled for it, but I was a hair too late and just got caught."

Uemura, the son of famous longboard surfer China Uemura, described yesterday's conditions as "about as tough as it gets."

"Just the winds alone," he said. "You had to paddle like 100 yards right into it. That was one of the hardest things."

Honolulu firefighter Kamaki Worthington placed third, and France's Peyo Lizarazu was fourth. Worthington received a $1,000 bonus from Da Hui for "The Biggest Move" award.

FINAL RESULTS

1, Kai Lenny (Hawai'i). 2, Kekoa Uemura (Hawai'i). 3, Kamaki Worthington (Hawai'i). 4, Peyo Lizarazu (France). 5 (tie), Ekolu Kalama (Hawai'i) and Bonga Perkins (Hawai'i). 7 (tie), T.J. Saeman (California) and Aaron Napoleon (Hawai'i).