Starting at 7am, the professionals took the plunge at Corrigans Beach for a 1.9km swim before a 90 km bike ride and 21.1km run.

Appleton, who won the 2012 and 2013 events, finished in three hours, 57 minutes and 29 seconds and was the only entrant to break the four-hour barrier.

Peter Robertson finished second in the men's race in four hours, three minutes and 21 seconds and was followed by Per Bittner in four hours, six minutes and 48 seconds. 

Van Vlerken won the women's race in four hours, 25 minutes and 47 seconds and just pipped Liz Blatchford who finished in four hours 25 minutes and 51 seconds.

Mary Beth Ellis rounded out the top three in four hours, 29 minutes and 31 seconds.

Appleton, 24, used his prowess on the bike and never looked back.

"It feels really good, I love Batemans Bay and I've been out here four years now and it's a happy hunting ground for me," Appleton said.

"It's nice to come back and get that top spot.

"I knew there were some fast runners in the field and I wanted to put pressure on with the bike.

"I thought I did that well for the first 60 kilometres but with about 25 to go my wattage started to go down a bit and I sort of went in to damage control."

Van Vlerken, who is from the Netherlands, raced at the Asia-Pacific Ironman Championship last weekend and backed up her second with a win at Batemans Bay.

"It's the first time I've been here, I've done a lot of Challenge events through Europe," Van Vlerken said.

"It's not normal, there's hardly anybody who does the half-distance a week after an Ironman.

"I have done it the other way around before but it was my boyfriend's (Per Bittner) idea."

Van Vlerken and Blatchford went toe-to-toe in the run and she pulled away in the final stretch.

"I just wanted to stay with her because it was a good pace," she said.

"I worked hard on the bike to close the gap.

"I said to her (Liz Blatchford) 'hey girl you go, I did the Ironman last week' but it was a mental race.

"All three of us are the same I guess." 

Seventeen-year-old Mitchell Cunningham won the sprint ahead of Reza Shahami and Broulee's Daniel Lloyd Jones.

Sarah Gardner won the women's sprint ahead of Lauren Elliot and Jacki Barnard.

Cunningham, from Gerroa, said he was pleased with his time.

"It was a good hit out before nationals," Cunningham said.

Lauren Griffin, 15, had the fastest time on the enticer course in 37 minutes and 21 seconds.

She finished ahead of Emily Kempson and Mikea Mbonzi Geamch.

"I was happy with my time, it was my first race back from injury," Griffin said.

Liam Meadham won the men's enticer ahead of Jack Wallis and Brendan Jones.