The Dutch master coach cited Chalmers' stunning 100m freestyle Rio Olympic gold as one of his successful tenure's highlights after announcing he would step down in September.

At just 18, Chalmers stunned the world - and clearly Verhaeren - when he became Australia's first 100m freestyle Olympic champion since Michael Wenden in 1968.

"Kyle's 100m freestyle is the eye catcher," Verhaeren said when asked to list his highlights.

"To have the Olympic champion after God knows how many years is very impressive because before that Australia had great potential (to win gold) but to actually get the win in the 100m was incredibly special."

And Verhaeren predicted more surprises to come next year, saying Australia's rising stars would only benefit from the Olympic postponement.

He cited Chalmers as a classic example of the difference a year can make in an emerging swimmer's development.

"The good news is the young ones coming through are a year older, sometimes a year makes a hell of a difference," said Verhaeren, who steered Dutch greats Pieter van den Hoogenband and Inge de Bruijn to multiple Olympic gold.

"Look at Kyle Chalmers. In 2015 he was a relay athlete. The next year he wins.

"If the Olympics were a year earlier he wouldn't have been an Olympic champion.

"We have a few younger athletes in the same boat who are capable of a high level of performance.

"To them that additional year is a gift - (they are) getting stronger with more training (and) more mature."

Overall Verhaeren believed the Dolphins were in good shape ahead of the 2021 Games despite the huge disruption caused by pool closures during the coronavirus shutdown.

"The good news is no one retired (after the postponement). We still have the people that were good for medals at the (2019) world championships still around," he said.

"It is a challenging time ... (but) we have a build-up phase until August.

"From that moment they can start the training they are used to."

Rohan Taylor - three-time Olympic gold medallist Leisel Jones' former coach - will take over the Dolphins reins from Verhaeren at Tokyo before a world-wide search for a full-time replacement.

Australian Associated Press