South Korean swimming champion Cho Oh-ryun, who earned the nickname "Asian Seal" after winning four gold medals at Asian Games, has died of a heart attack. He was 57.

Cho was found lying on the floor of his residence in Haenam, South Jeolla Province, and was rushed to a nearby hospital at about eleven a.m. Tuesday. He was pronounced dead at 12:45 p.m.

The star swimmer won gold medals in the 400-meter and 15-hundred-meter freestyle events at the 1970 and 1974 Asian Games.

In 1980, he swam across the Korea Strait, a 48-kilometer strip of water between Korea and Japan. Two years later, he swam the Dover Strait between Britain and France.

In 2005, Cho swam the 87 kilometers between Ulleung Island and the Dokdo islets in the East Sea with his two sons.

The legendary swimmer was preparing to repeat the challenge of swimming across the Korea Strait next year.