The Two-Person Keelboat (SKUD18) action saw a battle emerging between Australian crew Daniel Fitzgibbon/Liesl Tesch and Britain's Alexandra Rickham/Niki Birrell.
The Australians were quickly into their rhythm and produced a strong performance to win the opening race, with the Brits coming home in second ahead of USA's Jen French and JP Creignou.
The top two placings were reversed come the second race, however, with Birrell and Rickham resuming their private battle with the Australians before edging clear of their rivals, with Canadian pairing John McRoberts and Stacie Louttit in third.
In the Single-Person Keelboat (2.4mR) class there was more British early success, with Helena Lucas topping the early standings courtesy of a second place in race one and a victory in race two.
She will likely face fierce competition as the regatta progresses, although the hopes of French world number one Damien Seguin suffered an early blow when he was disqualified from the second of Saturday's two races following an official protest by Paul Tingley of Canada over an incident on the start line.
Seguin had won race one but was found to be at fault in the second race.
Beijing 2008 gold medallist Tingley failed to challenge the leaders - finishing sixth in race one and seventh in race two.
In the Three-Person Keelboat (Sonar) class, Australian trio Colin Harrison, Jonathan Harris and Stephen Churm lead the early standings after following up a victory in race one with a third-place finish in race two today.
Following the day's racing Australia's Sonar skipper Colin Harrison was pleased with the result, and the weather, saying: 'We had perfect sailing conditions today - probably one of the best sailing days I've ever had at this venue.'