After competing in a wide array of the world’s exotic aquatic locales, Rhys Mainstone is quickly becoming a fan of Hawaii’s favorable ocean conditions.

As hundreds of onlookers made their way onto Waikiki Beach on Monday morning to start the Labor Day holiday amid light and variable winds and sun-soaked sand, the 23-year-old swimmer was hard at work defending his title.

Mainstone, a professional athlete from Perth, Western Australia, claimed his second consecutive Waikiki Roughwater Swim along Oahu’s south shore. Mainstone crossed the finish line in 48 minutes and 10 seconds, edging Aussie George O’Brien (48:22) by what amounted to just a few strokes. Fellow Australians Ridge Grimsey (50:47) and Malcolm Allen (50:54) battled in the race for third, while Kacy Johnson (51:10) of Honolulu turned in the top time by a local competitor en route to finishing fifth overall.

"We’re all (swimming at about) the same speed, so it’s all about coming over the reef and catching a wave," said Mainstone, who did indeed ride a small ocean bump to add some breathing room ahead of O’Brien as the two sprinted through the Kaiser Channel. "Whoever catches that last wave was going to win, so I was lucky enough to come away with a win for the second year in a row. I think I’m on to something. Let’s see what happens next year."

More than 1,100 competitors began the 44th annual competition at San Souci Beach adjacent to the Waikiki Natatorium and completed the 2.384-mile event at Duke Kahanamoku Beach fronting the Hilton Hawaiian Village. The trapezoidal course took swimmers 0.42 miles out into open water, 1.44 miles along a path parallel to Waikiki Beach, and 0.52 miles back into shore.

"We were side by side throughout the entire race, and we both wanted to get on a wave. Rhys got a hold of a few more than I did, and I just couldn’t catch him," said O’Brien of the home-stretch sprint turned in by the friendly rivals. "He was too quick for me today. We got a good start, and he was on my feet around the first buoy. At the start, we were flying — the current certainly wasn’t against us."

Mainstone’s globe-trotting has taken him from Hawaii to Hong Kong — where he won the FINA 10-kilometer Marathon Swimming World Cup last year — and back to his hometown of Perth earlier in 2013, where he picked up $15,000 by winning the BHP Billiton Aquatic Super Series Open Water Challenge. Mainstone competes under the banner of Black Dog Institute, an Australian not-for-profit facility dedicated to helping men deal with mental health and depression-related issues.

"September is ‘Exercise Your Mood Month,’ so we’re out here exercising and having a great time," Mainstone said.

Miranda Bell of North Rockhampton, Queensland, Australia, was the top female finisher (53:05) after fending off runner-up Luane Rowe (53:28) of Oakland. Lia Foster (59:56) finished 46th overall, and was the first local female swimmer to cross the line.

"I didn’t make it up to the boys’ pack, so I was a bit back from them," said Bell, a member of Australia’s Lifesaving Team. "I had a really good swim, and it felt good; hopefully I can come back next year."

Competitors needed to complete the course in 2 hours, 40 minutes or less, and wear a swim cap throughout the entire race in order to be deemed an official competitor. Participants were divided into five heats, which took off at five-minute intervals, with the "A" group composed of elite swimmers — prior overall and division winners as well as current NCAA and high school All-Americans — starting the competition.

As one of the world’s largest and most prestigious roughwater swimming events, the Waikiki Roughwater Swim attracted participants representing countries from Asia to Europe. The diverse field included swimmers of all ages and experience levels, from casual competitors to world-class and Olympic-caliber athletes.

Kosuke Kitajima, a decorated Olympic swimmer from Japan, made the trip to compete in his second Waikiki Roughwater Swim and finished 13th overall (53:31) while winning the men’s 30-34 age group. The 30-year-old won gold medals in the 100- and 200-meter breaststroke at both the 2004 Athens and 2008 Beijing Olympic Games, and briefly held the world record in the 100-meter breaststroke. After picking up a total of seven Olympic medals over his competitive career, Kitajima said that he is "too old" to compete at such an elite level, and instead is "having fun" by participating in events such as Monday’s.

"Maybe I’ll be back next year; it’s a lot of fun," said Kitajima as he balanced an ice pack on his shoulder. "I’m getting old!"