WATER SPORTS - Head coach Jacco Verhaeren wants a hard competitive edge from Australia's swimmers at Budapest's World Championships as his team looks to rebound from last year's under-performing Rio Olympics.

The 'Dolphins' want to up their game when the world championships start on Sunday after winning three gold medals, four silver and three bronze in Rio, but well under their tally projections after going into the Olympics with eight world ones.

Not one of those top rankings was converted into an Olympic gold medal as world leaders including Cate Campbell and Cameron McEvoy succumbed to the crushing weight of home expectations.

Australia finished second on the swimming medal tally, but was a distant 23 medals away from the dominant United States with their 16 gold, eight silver and nine bronze.

Olympic 400-metre freestyle champion Mack Horton is back to renew his feisty rivalry with Chinese superstar Sun Yang and Emily Seebohm, Mitch Larkin and Bronte Campbell will be defending their world crowns in Hungary.

But Rio 100m freestyle gold medallist Kyle Chalmers is recovering from heart surgery and is missing along with team elders Cate Campbell and James Magnussen, who are taking time out.

Dutchman Verhaeren has switched Australian swimming's approach to international competition with important lead-up meets scheduled closer to the bigger events in a bid to toughen up his swimmers.

"We certainly had some great wins (in Rio), but we also had some losses, undoubtedly," Verhaeren said.

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