Jocko MacKenzie completed high school at Rochester, Minnesota, where he was named a High School All-American swimmer in 1943-44 and 1944-45. At Carleton he was undefeated in four years of swimming competition, including victories over Big Ten Champions. Specializing in the 60 and 100-yard free style events, he set an astounding 111 pool, varsity and conference records. He stands virtually without challenge as the greatest swimmer in Carleton history.

MacKenzie continued swimming with the New York Athletic Club and was named to the AAU All-American team in 1953. Shortly thereafter he entered the U.S. Marine Corps as a career officer. He continued his athletic activities in the Marines, participating in intramural and interservice volleyball, football, swimming and sport parachuting.

Jocko was named to the AAU All-American Masters Swimming Team in 1974. In 1974, 1975 and 1976 he was a Masters champion and national record holder in AAU Masters swimming competition. In 1976 he captured three gold medals in the Senior Olympics.