The feature swim, The Ruby, saw swimmers take off from Waterfall Creek and swim 2.5km around nearby Ruby Island and back to shore.
It was won by local Rio Olympian Tony Dodds in a time of 31.08, about a minute off the course record.
Mr Dodds said he had only signed up for the race the night before.
"I was going to go for an open water swim anyway, so I thought I may as well join the other 200-odd people here."
He said it was a "good hit-out" before an International Triathlon Union event in Adelaide next weekend.
The 3.8km Big Ruby was won by German man Hartmut Anneken in a time of 54.43, while the inaugural 10km Ruby10 was won by Steven Prescott, of Ashburton.
Wanaka’s own Leo Staufenberg won the 1.2km Return of the Jetty race in a time of 18.04, and was not the only local winner, as Cruz Morland won the 600m Island swim in 12.20.
Cromwell’s Flynn Stuart (10) won the 200m Little Gems race in 3.51.
Officially it was the fourth time the event had been held, although it was cancelled in its debut year in 2015 due to bad weather.
