Australia's men's water polo team have sensationally upset Hungary by one goal to secure a quarter-final spot at the Olympics.

The Sharks' Nathan Power scored the match-winner with just 46 seconds remaining in Saturday's fixture at the Paris Aquatic Centre.

The 9-8 victory lifts Australia to second in their group with three wins and one loss for the tournament.

With one group game remaining, against winless Japan on Monday, the Sharks are assured of reaching the quarter-finals.

The win against nine-time Olympic champions Hungary was secured by Power converting from close range.

The Sharks scored three goals to one in the final quarter to overcome the Hungarians and their influential forward Krisztian Manhercz, who scored four goals in the match.

Australia's Power logged two goals, as did captain Blake Edwards and Milos Maksimovic, whose scores included the sweetest of reverse backhanders from about seven metres out in the second period.

Luke Pavillard, Marcus Berehulak and Chaz Poot also scored in Australia's win.

The Sharks raced to a 4-2 lead in the second quarter but were in strife as Hungary rallied to hold a 5-7 advantage in the third.

The Australians trailed 6-7 at the last break before producing a stunning last-term surge, capped by Power's late heroics.