Tom Slingsby and Team Australia have won the Spanish leg of the SailGP campaign on a wild afternoon on the Bay of Cadiz.

The Australians eased to victory in the podium race after Sir Ben Ainslie's Great Britain boat capsized just after the start, effectively knocking the United States team, skippered by Australian Jimmy Spithill, out of contention.

The win on the Bay of Cadiz allowed the Aussies to vault back into the lead in the season standings heading into their home regatta in Sydney in mid-December.

The anticipated heavyweight showdown in the podium race among three of the world's best skippers never materialised.

Ainslie's 50-foot catamaran nosedived shortly after the start and Spithill had to turn so suddenly to avoid a collision that his catamaran crashed off its foils, triggering the emergency stop systems.

During the time it took for the systems to restart, Slingsby had sailed away for his third victory in six regattas this season.

"We're stoked with the day. It couldn't have gone better for us," said Slingsby, who for the second time this season bounced back from a last-place finish to win a regatta.

"It looked like they got a big gust and got a little bit high on the foils. I just saw them go into a huge pitch-pole right in front of us.

"The goal was to avoid them and then we didn't really realise what happened to Team USA.

"We realised we had a big lead and we just had to nurse our way around the track."

Spithill, a two-time America's Cup winner, was able to get going again and finished the race to strengthen Team USA's spot on the leaderboard.

Australia lead the eight-team fleet with 45 points, followed by the United States and Japan with 44 each and Britain with 40.

The rest of the fleet is New Zealand with 36 points, Spain 35, Denmark 33 and France 31.

After the Sydney regatta, the season championship will be decided in San Francisco from March 26-27 when the top three teams will sail for the $1 million ($A1.4m), winner-take-all championship.

The Aussies won the top prize during the inaugural 2019 season.

"It's a nice feeling to finish the European leg in front," said Slingsby, who won a gold medal at the 2012 London Games.

"Everyone's joking we're the Ricky Bobby of the fleet. We're either first or last... I'm happy we're on form in the final event and we're heading into Australia with the lead."

The Aussies won just one of five fleet races during the weekend but never finished lower than fourth place in the other races.

With the wind blowing above 20 knots, Spithill skippered the American boat into the podium race for the fourth time this season.

"Today was definitely on the edge. You're really in avoidance mode," Spithill said.