Natalie du Toit claimed her 12th Paralympic swimming gold at the London 2012 Games on Tuesday as China's Xu Qing said a lucky shark tattoo had helped him break another world record in the pool.
Du Toit won the women's 400m S9 freestyle at the Aquatics Centre, the 28-year-old South African taking her 12th career gold in a time of 4:30.18.
She was one of several stars who successfully defended their Beijing 2008 golds on a busy night in the pool, including Xu, Mirjam de Koning-Peper of the Netherlands, Britain's Heather Frederiksen and Konstantin Lisenkov of Russia.
Du Toit finished comfortably ahead of Britain's Stephanie Millward and Australia's Ellie Cole, who nonetheless set new European and Oceanian records respectively for the silver and bronze medals.
The trio finished in the same positions in the 2010 world championships final.
Du Toit dedicated her victory to Cathy Doyle, the Central Gauteng Aquatics president who died in January following a long illness.
"That race was for Cathy Doyle. She was our CGA president. She passed away a few months ago. She was supposed to be officiating tonight," said du Toit who is competing in her final Paralympics.
"Because she has done so much for me in my life, I just want to dedicate this medal to her and her family. Thank you to them.
"She was at the world championships on the side of the pool. Sometimes I try and picture her sitting on the chair.
"This was one of the safe races. The longer the distance, the better for me. I start getting my stride and I start pulling away."
Xu said he was spurred on by his body art and a little luck from his friends as he broke a second world record at London 2012.
He won in the S6 men's 50m freestyle gold in a time of 28.57 seconds, the first swimmer to go below 29 seconds in the event.
"In China we say we borrow luck from our friends, and before a race I always borrow some luck from my team-mates," he said.
"And I have a lucky tattoo on my right shoulder. It is in the shape of the shadow of a shark. Sharks are fast and aggressive and that is how I like to swim.
"I didn't think I could beat my own world record, but my coach said that this was the race for me, I could do it. And he was right."
He also won the S6 200m individual medley on Monday in a world best time.
De Koning-Peper set a Paralympic record of 34.77 seconds to win the women's S6 50m freestyle, beating 17-year-old British swimming star Ellie Simmonds, the home nation's poster girl for the Games, into bronze position.
"It was a great swim. I was very nervous this time, but I think it was very good," the Dutchwoman said.
Simmonds, who has already won two London 2012 golds, added: "This is my fourth-best event, so coming out with a bronze is great."
World record holder Lisenkov won the S8 men's 100m backstroke in a new Paralympic record of 1:05.43.
"If you break the record, the medal will come," he said.
"I'm emotional. I've trained so hard for this."
World record holder Frederiksen retained her Paralympic S8 women's 100m backstroke title, claiming Britain's fifth swimming gold.
South Africa's Natalie du Toit competes during the Women's 400 metres freestyle final S9 category during the London 2012 Paralympic Games. Du Toit claimed her 12th Paralympic swimming gold.