A short distance from where swimmers enjoyed a Sunday morning swim in the Han River, a man had died just a week earlier, caught in a whirlpool created by a submerged weir. “Even the day before the incident, a couple of young people were swimming dangerously close to the sluice gates at the submerged weir,” said Sohn, 63, as he emerged from the river after swimming underneath Jamsil Bridge in Seoul. Even as he spoke, dozens of people could be seen swimming in the river on the southern side of the bridge. “This is one of the few places where people can swim in open water,” Sohn said. “The number of people coming here to swim has risen sharply since triathlons began gaining popularity last year.” But as more people take up open-water swimming as a hobby, serious safety concerns are being raised. The area near Jamsil Bridge was the scene of a fatal accident on Aug. 2, when a man in his 30s was caught in a whirlpool and pulled into the sluice gate. Beneath the bridge, close to the swimming area, is a submerged weir that regulates the flow of water downstream from the upper reaches