Kyle Chalmers wins silver in 100m freestyle

Kyle Chalmers says his silver medal is bitter-sweet, falling a finger-nail short of defending his Olympic 100-metres freestyle title.

Chalmers was pipped by American Caleb Dressel by just 0.06 seconds in a thrilling Thursday final.

"To get second is amazing, to back it up after gold in Rio," Chalmers said.

"The five-year journey has been really challenging and so to get silver is special.

"But to be so close, it does hit home a little bit."

Chalmers unleashed his trademark late surge, coming from third at the turn to draw level with Dressel.

But the American rallied to win in 47.02 seconds followed by Chalmers (47.08) and Russia's Kliment Kolisnikov (47.44).

"I swim with my eyes closed which is half my problem," Chalmers said.

"More to be in my own mind frame, have my eyes closed and put all my energy into the race.

"I started well, the start felt pretty good, I felt pretty strong and comfortable going out and gave it everything I could.

"There's nothing I could have done better.

"To be half a second faster than Rio. I guess there's not many people who do a fastest time at an Olympic Games."

The Adelaide-based flyer was seeking to become the first Australian to claim double gold in the highly-anticipated event.

Jon Henricks (1956), John Devitt (1960) and Michael Wenden (1968) are Australia's other 100m freestyle champions.

Only four swimmers in Olympic history have won back-to-back 100m freestyle titles.

And Chalmers faced a bumpy path to Tokyo, having left shoulder surgery last November.

"I have had 12 cortisone injections in my left shoulder, and the surgery - and that's just on the left shoulder alone," he said.

"I have had ankle problems, three epidurals in my back, cortisone in my right shoulder.

"That's just the physical side of things.

"Everyone has challenges.

"But to stand up and go for an equal-best time in an Olympics final when it counts the most with all the pressure and expectation on me, it is special."