Zhang Lin improved Grant Hackett's four-year-old 800 meters freestyle world record by more than six seconds and won China's first ever men's gold at the world swimming championships. Zhang powered home in seven minutes, 32.12 seconds on Wednesday to break Hackett's record of 7:38.65.

Tunisia's Ous Mellouli, overtaken by Zhang at 200m mark, picked up the silver in 7:35.27 and Canadian Ryan Cochrane was third in 7:41.92.

American Michael Phelps responded to a stunning loss on Tuesday with a world record Wednesday.

Zhang Lin shows the gold medal after the men's 800m freestyle swimming final at the World Championships in Rome, Italy, July 29, 2009. China's Zhang Lin broke the world record to win the men's 800 meters freestyle gold at the World Championships on Wednesday. Zhang clocked seven minutes 32.12 seconds to break Australian Grant Hackett's previous mark of 7:38.65

Phelps, beaten by Germany's Paul Biedermann in the 200m freestyle final, set a world record in the 200m butterfly with a time of one minute, 51.51 seconds, shaving more than a half second off his previous mark of 1:52.03.

South Africa's Cameron van der Burgh broke the mark he set in the semifinals to win the 50m breaststroke.

Earlier, Germany's Daniela Samulski broke the women's 50m backstroke world record in the first semifinal and Russia's Anastasia Zueva bettered the minutes-old mark in the second semifinal.

Italy's Federica Pellegrini beat her own world record to win the women's 200m freestyle to complete a golden double.

The 20-year-old Olympic champion splashed away in the second half of the race to clock 1:52.98 seconds, 0.68 seconds off the previous mark she set in Tuesday's semis.

Zhang Lin improved Grant Hackett's four-year-old 800 meters freestyle world record by more than six seconds and won China's first ever men's gold at the world swimming championships. Zhang powered home in seven minutes, 32.12 seconds on Wednesday to break Hackett's record of 7:38.65.

Tunisia's Ous Mellouli, overtaken by Zhang at 200m mark, picked up the silver in 7:35.27 and Canadian Ryan Cochrane was third in 7:41.92.

American Michael Phelps responded to a stunning loss on Tuesday with a world record Wednesday.

Zhang Lin shows the gold medal after the men's 800m freestyle swimming final at the World Championships in Rome, Italy, July 29, 2009. China's Zhang Lin broke the world record to win the men's 800 meters freestyle gold at the World Championships on Wednesday. Zhang clocked seven minutes 32.12 seconds to break Australian Grant Hackett's previous mark of 7:38.65

Phelps, beaten by Germany's Paul Biedermann in the 200m freestyle final, set a world record in the 200m butterfly with a time of one minute, 51.51 seconds, shaving more than a half second off his previous mark of 1:52.03.

South Africa's Cameron van der Burgh broke the mark he set in the semifinals to win the 50m breaststroke.

Earlier, Germany's Daniela Samulski broke the women's 50m backstroke world record in the first semifinal and Russia's Anastasia Zueva bettered the minutes-old mark in the second semifinal.

Italy's Federica Pellegrini beat her own world record to win the women's 200m freestyle to complete a golden double.

The 20-year-old Olympic champion splashed away in the second half of the race to clock 1:52.98 seconds, 0.68 seconds off the previous mark she set in Tuesday's semis.