Three-time defending SailGP champion Tom Slingsby of Team Australia rebounded from two poor performances to win the third fleet race and stay in contention in the inaugural Canada Sail Grand Prix Halifax.

The Australians are sixth overall in the 10-boat fleet heading into Sunday's final two fleet races. The top three boats advance to the podium race.

Giles Scott skippered Great Britain into first place with finishes of 3-5-2 for 23 points, with season leader Peter Burling of New Zealand second with 22 points and Nicolai Sehested of Denmark third with 21.

Slingsby showed how quickly things can change, especially on a day with shifty, gusty conditions. The Australians finished eighth and sixth in the first two races before shooting the line at the start to get into great position and then finishing ahead of Britain and Canada.

"We were in a battle all day, it felt like," Slingsby said.

"It felt like we sailed the boat somewhat well today but we just weren't in phase with the shifts and that responsibility falls on my shoulders.

"We've got the talent, we've got the skill set, we just need to put it all together. It was nice to finish well today.

"This puts us in with a chance heading into day two of making the final and that's what we needed."

Slingsby got caught in what he called a "dog fight" in the second race with fellow Australian Nathan Outteridge, who is skippering the Swiss team.

Slingsby said Outteridge made several aggressive moves that pushed the two teams into a match race, which the Aussies felt was intended to sabotage them.

"We felt we were a bit unlucky out there today and we had a few bad instances in the second race," Slingsby said.

"I was pretty frustrated with my old mate Nath. He chose to luff us about 15 times in a 20-second period.

"He could have chosen to go straight into the reach mark and keep his position, but instead chose to get into a dog fight with us to push us back in the fleet."

Slingsby, an Olympic gold medallist and former America's Cup champion, skippered the Australians to the first three season championships in tech baron Larry Ellison's global league, when the winner-take-all prize was $US1 million ($A1.5 million).

The prize money has been doubled this year.