The women's world number three finished with a total of 12.50 to edge out Costa Rica's Brisa Hennessy (12.20) on Sunday at Tsurigasaki Beach.

Earlier in the day, Culburra Beach surfer Owen Wright also impressed, progressing to round three with victory in his heat earlier in the day, scoring 10.40 to edge out Morroco athlete Ramzi Boukhiam (10.23).

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The result continued Fitzgibbons' red-hot recent form, which included winning gold at last month's ISA World Surfing Games and claiming the World Surf League title in May.

Fitzgibbons and Wright form half of Australia's Irukandjis Olympic surf team, with Stephanie Gilmore also securing a heat win on day one of competition. Julian Wilson finished fourth in his heat.

Sunday marked surfing's official debut at an Olympic Games, with the competition held in waist-to-chest height conditions.

A stronger surf is predicted on Monday, as Japan braces for a typhoon, with bigger sized waves forecast for the remainder of the competition.

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