German world champion Florian Wellbrock added Olympic marathon swimming gold to his 1500m bronze with a dominant performance in hot conditions in Tokyo Bay on Thursday.
Wellbrock swam the 10 kilometres (six miles) in 1hr 48min 33.7sec, more than 25 seconds clear of Hungary's Kristof Rasovszky (1:48:59.0). Italy's Gregorio Paltrinieri took the bronze in 1:49:01.1.
Wellbrock and Paltrinieri became just the second and third athletes to win pool and open-water medals at the same Olympics, after Tunisia's Oussama Mellouli grabbed marathon gold and 1500m bronze at London 2012.
"The first seven kilometres was really easy," said Wellbrock. "The water wasn't really warm, so then I keep up the pace and the last leg was horrible.
"The temperature today was the biggest competitor. I beat it and I beat everything in this race."
The double by Italy's Paltrinieri, who took silver in the 800m freestyle, is all the more remarkable after his build-up to the Games was hampered by a bout of glandular fever.
"I didn't arrive here in the best condition because of an infection that I had the last month, so I knew it was pretty tough for me to compete with these guys," Paltrinieri said.
"But I'm on the podium so that's all right."