Gold medalist United States' Caeleb Dressel poses with his gold medal following the men's 50m freestyle final at the World Swimming Championships in Gwangju. Photo: Lee Jin-man/AP Photo

GWANGJU  Caeleb Dressel confirmed his star status with a record medal haul at the swimming world championships which concluded Sunday in Gwangju while there was a hint that compatriot Katie Ledecky is not super human after all.

But with the eyes of the sport now turning to the Tokyo 2020 Olympics a year from now, doping remains a shadow which cannot be escaped completely.

America's Dressel not only erased the great name of Michael Phelps from the world record books in the 100-metre butterfly but became the first athlete to return home from a championships with eight medals (six golds and two silver), one more than two years ago in Budapest.

"It was not easy in '17, and it was not easy this year," Dressel said. "I don't want it to be easy, I really don't."

The swimming worlds offers more medal chances than in Phelps' time with the introduction of medley relays but the Games next year has a tighter programme due to the total number of swimmers that can be invited.

"As a team, this is kind of a weird year because we don't have a trials leading up to this meet," Dressel said. "We are light-years ahead of where we were in 2015, and we had a great meet in Rio (2016), so if this is where we're at heading into Tokyo, I think we'll be very dangerous next year."

With multiple individual winners the US were the top nation in the pool but Ledecky, virtually unbeatable in the distance freestyles, had to settle for just one gold in the 800m.

She did add minor medals along with two scratches as illness ravaged her hopes of a distance sweep.

"I took it out like I usually do, and just kind of relied on my training to bring me home," Ledecky said of pipping Italy's Simona Quadarella in the final sprint.

"I just tried to stay calm and relaxed from the 500 to the 750, and decided in the last 100 when I was going to make a move. (From there) I just put my legs into it and got my hand on the wall."

Outside of the US, teenagers Maggie MacNeil of Canada, Kristof Milak of Hungary and Ariarne Titmus of Australia, who beat Ledecky in the 400m free, also established themselves on the global stage with gold.

Doping remains an issue, however, with China's Sun Yang subject to podium protests by other athletes. Sun served a secret three-month doping ban in 2014 and is currently competing despite a case at the Court of Arbitration for Sport (CAS) over doping test samples being smashed in a confrontation with officials last year.

Australia also made the headlines for the wrong reasons as it emerged Shayna Jack tested positive for doping shortly before the championships.

The 20-year-old protested her innocence after a sample revealed traces of Ligandrol, which can help repair muscle, was found in her sample.

But Swimming Australia and the country's Anti-doping body bickering over who could reveal the ban and when did not give an impression of transparency.

That delighted some Chinese media who pointed out the apparent hypocrisy of Mack Horton, an Australian swimmer, being one of the leaders of the protests against Sun.