The Australian breezed to victory in Tuesday night's heats at the Tokyo Games as American challenger Caeleb Dressel and Italian flier Thomas Ceccon also impressed.

Ceccon was quickest through the heats in 47.71 seconds followed by Dressel (47.73) and Chalmers (47.77).

Chalmers is the sole Australian defending an individual gold medal in Tokyo.

And the 23-year-old had already showed ominous form in rapid swims for Australia's bronze medal winning 4x100m freestyle relay team.

In his heat, Chalmers was mid-pack at the turn before reeling in the field with his trademark late burst.

The South Australian will return to the pool for a semi-final on Wednesday, as will teammate Brianna Throssell, who was ninth-fastest through the 200m butterfly heats.

In the men's 800m freestyle, Jack McLoughlin - already with a silver medal from the 400m freestyle - was sixth-quickest into the final, finishing a solid third in his heat.

Zac Stubblety-Cook evidenced his medal prospects in the men's 200m breaststroke with a standout swim in the heats.

Stubblety-Cook clocked 2:07.37 to dead-heat with Arno Kamminga from the Netherlands.

Stubblety-Cook, who entered Tokyo with the world-leading time this year in the event, and Kamminga topped the heats with Australia's Matt Wilson 10th quickest and into the semi-finals.

Australia's 4x200m freestyle relay team of Alexander Graham, Mack Horton, Elijah Winnington and Zac Incerti were second-quickest in heats, with Great Britain almost two seconds clear of the field.

Australian Associated Press