They led from the starting gun to the finish line in the first race and were never under threat.

The Australian crew of Daniel Fitzgibbon and Liesl Tech took second place, with Canada's John McRoberts and Stacie Louttit in third, edging ahead of Alexandra Rickham and Niki Birrell of Great Britain, who had led the class overnight.

The USA pair continued to impress in the second race, taking the lead after Fitzgibbon and Tesch  incurred a penalty turn for hitting a marker.

Fitzgibbon and Tesch now lead by a single point from Rickham and Birrell in second and French and Creignou in third.

'We don't like being pushed down the leaderboard,' Rickham said. ' We're hoping this was our worst mistake. We're going to be plugging away; keeping our routines going.'

Meanwhile, there was a change at the top of the leaderboard in the Single-Person Keelboat (2.4mR) class, with Germany's Heiko Kroger recording a fifth and a first place to take the top spot.

Both races of the day involved close scraps between five boats. The top four boats crossed the line almost simultaneously in the first race, with the Netherlands' Thierry Schmitter snatching victory from the defending champion, Canada's Paul Tingley, Great Britain's Helena Lucas in third and France's Damien Seguin in fourth.

In the second race, overnight leader Lucas dropped back to 11th place after taking a two-turn voluntary penalty for an incident at the first mark, allowing Kroger, Seguin  and Peurto Rico's Julio Reguero to edge away.

Kroger held on to win with Reguero in second and Finn Niko Salomaa coming through for third.

Kroger now leads the class by one point from Schmitter in second and four ahead of Lucas.

In the Three-Person Keelboat (Sonar), Dutch trio Udo Hessels, Marcel van de Veen and Mischa Rossen were the standout performers of the day.

They followed up a second-place finish in Race 3 with a bullet  - Sailing terminology for a victory - in Race 4 to close the gap on overnight leaders Colin Harrison, Jonathan Harris and Stephen Churm of Australia.

And there was worse news for the Australian trio later in the day when they were penalised by race officials and demoted down the overall field.

A jury of experts heard a protest made by John Robertson, Stephen Thomas and Hannah Stodel of Great Britain and decided that in the first race the Australian crew had been guilty of an infringement. As a result, they were penalised 15 points.

A separate protest by Greek trio Vasilis Christoforu, Theodorous Alexas and Anargyros Notaroglu of Greece against Bruno Jourdern, Nicolas Vimont-Vicary and Eric Flageul of France resulted in the French crew being disqualified, as they dropped from third overall to sixth.