Olympic champion Park Tae-Hwan of South Korea stormed to victory in the men's 400 metres freestyle on Tuesday to retain his Asian Games crown.
Park, swimming in lane two, led from the start and never looked troubled, clocking 3:41.53 to finish ahead of Chinese pair Sun Yang (3:42.47) and Zhang Lin (3:49.15).
It was the South Korean's second gold of the Games after his win in the 200m freestyle.
Zhang, whom Park beat to the 400m freestyle gold at the 2008 Olympics in Beijing, will be bitterly disappointed with his swim, although he had complained of feeling tired ahead of the race.
Dubbed "Marine Boy" in South Korea, Park won three gold, a silver and three bronze medals in Doha four years ago.
His medal haul was the largest by a single athlete and he was named the most valuable player of the 2006 Games.