The ejection of Australian men's water polo vice-captain Thomas Whalan proved costly at the World Swimming Championships in Spain.

Whalan tussled with USA skipper Wolf Wigo after the Americans scored a goal early in the third period and both were benched by the referee. Neither player was sanctioned.

It was a big loss for Australia, taking away its strongest firepower at a crucial period in the game.

The Australians fought back to 8-5 down but the game ran away from the Sharks, losing 13-7, with the Americans winning the group comfortably.

Australia's campaign is now at crisis point as it will face European No.2 Croatia (who missed out by one goal from winning Group A) in the second round with only the winner going to the top-eight competition.

Head coach Erkin Shagaev said he couldn't take anything away from the USA.

"We have many players with a lack of experience at this level and it showed today," Shagaev said.

"It just wasn't our day."

Goalkeeper James Stanton made five saves and left-hander Trent Franklin scored two goals.

All matches went to order during the day with Croatia's 12-9 victory over Romania the most exciting of the day.

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