Victorian 21-year-old Brendon Smith has shot to gold-medal favouritism in the 400-metre individual medley - the first of three swim finals featuring Australians on Sunday.

Smith set an Australian record in his heat and was quickest into his final while the women's 4x100m freestyle relay team is an unbackable favourite to deliver a Sunday gold.

The relayers - and flagbearer Cate Campbell - are seeking a third consecutive OIympic title and will race after medal prospects Elijah Winnington and Jack McLoughlin contest the 400m freestyle final.

The forecast success at the pool comes on a hectic day for Australian Olympians, who will be in action across 22 sports.

World No.1 Ash Barty starts her Tokyo singles campaign against Spain's Sara Sorribes Tormo while Ajla Tomljanovic is also in action.

Barty paired with Storm Sanders on Saturday to easily beat Japan in their women's doubles opener.

Amanda Spratt will lead a high-quality Australian cycling team in the women's road race, but the Dutch start as overwhelming favourites.

The Olyroos, coming off their outstanding opening win over Argentina, meet Spain while Jessica Fox, chasing an elusive gold medal, has her first runs in the K1 preliminaries.

Surfing and skateboarding debut as Olympic sports with the men's and women's surf competitions scheduled to start at Tsurigasaki Beach.

Stephanie Gilmore, Sally Fitzgibbon, Julian Wilson and Owen Wright are Australia's surfing team.

Shane O'Neill is Australia's skateboarding entry, with the medals to be decided on Sunday.

The Boomers, after an impressive lead-up to the Games, take on Nigeria in men's basketball.

The Hockeyroos begin their Tokyo assault against Spain and the Kookaburras, fresh from a tough 5-3 win over the host nation, play India.

Australia must stage a major upset against the United States to keep their faltering softball campaign alive, while the Sharks play Montenegro in men's water polo.

Australian Associated Press