Zhang Yufei wins women's 200m butterfly and then returns to the pool to help China upset fancied Australia in 4x200m freestyle relay with World record.
Caeleb Dressel won the blue riband men's 100m freestyle as the United States celebrated two gold medals in the Tokyo pool on Thursday while China's women responded with two golds, and a World record, of their own in another thrilling day of swimming.
Alongside Dressel's triumph in the marquee event, fellow American Bobby Finke clinched the 800m freestyle with an impressive late surge.
China gained their first gold in the Tokyo pool with Zhang Yufei winning the women's 200m butterfly and then she returned to the pool to help her team upset the favoured Australians to win the 4x200m freestyle relay, setting a world record along the way.
Australia's Zac Stubblety-Cook took gold in the men's 200m breaststroke, also thanks to an incredible late surge to the finish.
World champion Dressel powered to victory in an Olympic record 47.02, finishing six hundredths of a second ahead of Rio winner Kyle Chalmers of Australia, with Russian Kliment Kolesnikov taking bronze.
Dressel went into the race as favourite and led from rising star Kolesnikov at the turn before holding off a strong finish from Chalmers to touch first.
It was Dressel's fourth Olympic gold but his first in an individual event having picked up two relay medals in Rio and the 4x100m freestyle relay in Tokyo.
“I wasn’t worried about anything at all ... it means a lot, I knew the weight was on my shoulders," said Dressel.
"It's a really tough year, it's really hard. So, to have the results show up, It really came together, so I'm happy," Dressel said.
In the 800 free, Finke pulled off a surprise win ahead of Italian world champion Gregorio Paltrinieri, who led all the way until the 750m turn when German Florian Wellbrock moved in front for the last length.
But Finke then made his late move and powered home in a time of 7:41.87. Wellbrock faded but Paltrinieri did not, the Italian, who had been a doubt for the Games due to illness, touching 0.24 seconds behind Finke to take the silver.
Ukraine's Mykhailo Romanchuk took the bronze medal.
Finke said he had to push hard when he saw Paltrinieri was clawing his way back towards the finish.
"I noticed when I was about 10 metres out that he was catching a little ground and that was all the motivation I needed," said the American.
Paltrinieri was the clear favourite last year before suffering with "mono," or mononucleosis, and its tiring effects.
"I didn't know how it would go, so being here on the podium, I wouldn't have bet a euro on it. I wouldn't have bet on it two weeks ago," he said.
China's biggest gold medal hope Zhang delivered in style -- taking control from the outset as she set an Olympic record of 2:03.86 to improve on her silver from the 100m butterfly.
Americans Regan Smith and Hali Flickinger took silver and bronze to win the country's first medals in the women's event since Sydney in 2000.
Zhang was soon back in the water and medalling again as part of the victorious 4x200m Chinese team, which left the Americans and highly-rated Australians trailing in their wake.
Australia had been the fastest qualifiers, and with double Tokyo gold medal winner Ariarne Titmus in their team were the heavy favourites to follow-up on their 4x100m gold.
Zhang kept China in front on the penultimate leg before handing over to Li Bingjie, who did well to hold off six-times gold medallist Katie Ledecky in the final metres as the United States had to settle for silver.
In the men's 200m breaststroke, Arno Kamminga of the Netherlands led at the 150m turn and was inside world record time as he fought with Finland's Matti Mattsson.
Stubbletly-Cook was third on the last turn, 1.2 seconds adrift of the lead, but then delivered an astonishing final lap to secure the country's fifth gold medal in the pool so far and the first for their men.
Kamminga was second, adding to his silver in the 100m breaststroke, with Mattsson taking bronze.
The gold was the first in men's breaststroke for Australia since Ian O'Brien in Tokyo in 1964, also in the 200m.