When Emeric Payer plunged into the pitch-black waters of Victoria Harbour at 4am on Monday, his coaches’ old jokes about his endurance were still fresh in his mind. A former competitive pool sprinter in the 50-metre freestyle, the 21-year-old was known to fade minutes into longer distance swimming events. But this changed when he completed a solo, unassisted 45-kilometre circumnavigation of Hong Kong Island in the record time of 10 hours, 22 minutes and 59 seconds. The Hong Kong-French swimmer...