Adam Peaty plans to complete his 'project 56' on Monday by becoming the first to swim under 57 seconds in the men's 100m breaststroke final at the world championships.

The 22-year-old has shaken up the event since taking gold at the 2015 worlds when he had broken the then-world record of 57.92 secs the previous April.

He has twice lowered it since -- once in the heats and again in the final -- en route and set a new mark of 57.13secs in winning the 2016 Olympic title.

Having swum 58.21secs in the 100m heats in Budapest on Sunday, then 57.75 in the semi-finals, Peaty says he can go faster in the final.

"I probably could have got out a little bit more, but you don't really want to empty the tank," he said after clocking the fastest semi-final time.

"As I was doing it, I could have gone faster again, there's always room to step up.

"That's what turns a 57.7 into a 57.1, but whether we get a 56 tomorrow or in three years, you don't know.

"How far can the human body go? That's the beauty of sport, we'll see what we get."

To mark his Rio success, Peaty had a lion tattooed on his left shoulder.

The lionheart wants to 'attack' not defend his 100m world title, then his 50m crown on Thursday.

Fresh from his emphatic victory in Sunday's 400m freestyle final, Chinese superstar Sun Yang will be racing again in Monday's heats and semi-finals over 200m.

Sun won the 200m title at the Rio Olympics and Britain's James Guy is the defending world champion.

It is set to get loud on Monday evening at Budapest's Duna Arena when local favourite Katinka Hosszu races in the women's 200m individual medley final having swum 2:07.14 in Sunday's semi-final.

"It's something amazing to swim here, the Hungarian swimmers have prepared for it, but this surpasses our imagination," admitted the home-crowd favourite.

"It's not sure there will be a world record, but it would be good," she added with one eye on her 2:06.12 world record in the 200m IM set in 2015.

Sarah Sjostrom of Sweden will defend her title in the women's 100m butterfly fresh from setting a world record on Sunday.

The 23-year-old became the first woman to swim the 100m freestyle in under 52 seconds in the 4x100m relay final as she clocked 51.71secs in her leg.

She was the fastest from the butterfly semi-finals over 100m.

Katie Ledecky, the world record holder, will be the star name in Monday's heats of the women's 1500m freestyle after winning two golds on Sunday.

The 20-year-old won the 400m freestyle final and then helped the United States win the 4x100m freestyle relay final.

Ledecky has set herself a punishing schedule in Budapest by racing in six freestyle races -- with two golds already in the bag.

Source: AFP