WATCH: Tennis stars Roger Federer and Lleyton Hewitt play tennis on speedboats in Sydney

Tennis stars Roger Federer and Lleyton Hewitt played a challenging match against each other on Monday. 

Not on a court, but on speedboats in the Sydney Harbor.

They each were in separate boats and started volleying the ball to each other as the boats sped through the harbor.

They may be professionals on the court, but the two had trouble finding their balance and lost quite a number of balls in the harbour. They occasionally did find their rhythm and managed to give quite the show to their adoring fans.

9News reported that the event was to promote FAST4, a new tennis format launched Monday night at the Qantas Credit Union Arena in Sydney, Australia.

FAST4 will see no advantages and lets, tie breakers will be at 3-3 and the first player to reach four games will win the set, which means tennis matches should end much faster.

Sources: ABC News, 9News, Sydney Morning Herald

Roger Federerlleyton hewittTennisSydney