Aussie Kyle Chalmers claims 100m freestyle silver in thriller

It was billed as the race of the world swimming titles in South Korea.

And the showdown between Olympic champion Kyle Chalmers and American superstar Caeleb Dressel didn't disappoint.

Even Chalmers couldn't complain after Dressel claimed 100m gold to defend his world title - but almost had to break the world record to do it.

In an extraordinary finish, Dressel clocked 46.96 seconds - just 0.05 off the world mark.

It was the fastest time ever in a textile suit.

Brazilian Cesar Cielo's 2009 world record of 46.91 was completed in a now banned supersuit.

Chalmers took plenty of consolation as he claimed silver in a personal best 47.08 - ranking him third in Australia's all-time list.

"I gave it my absolute all tonight. I could't really believe it (PB time) when I saw that and to see Caeleb go 46.9 is absolutely mind blowing," Chalmers said.

"It is really positive for me leading into Tokyo (Olympics)."

Dressel got his first win over Chalmers after the Australian earned bragging rights at the Rio Olympics and last year's Pan Pacs.

It marked the American's third gold of the meet and fourth overall.

Dressel became only the fifth man to win multiple world titles in the men's 100m freestyle.

Chalmers said the loss had already put a fire in his belly for Tokyo 2020.

"I think it does. We both swam pretty well tonight. We've had three good results now - Olympics, Pan Pacs and now worlds," he said.

"I enjoy racing against him. He is an unbelievable athlete, a great guy and I love being able to compete against the best guys in the world.

"At the moment he is that guy.

"It is about re-setting and putting as much effort as I can into the next 12 months to challenge him for that gold medal and defending my title."

Remarkably, Chalmers has now taken half a second off his personal best 100m time in the last three months.