Between 19, Spitz won nine Olympic golds, a silver, and a bronze; five Pan American golds; 31 Amateur Athletic Union (AAU) titles; and eight National Collegiate Athletic Association (NCAA) titles.
During those years, he set 35 world records, but two were in trials and unofficial.
Spitz also set a number of world records during the U. Olympic Swim Trials held in Chicago's Portage Park in 1972.
He was nicknamed "Mark the Shark" by his teammates.
In addition, Spitz finished second in the 100-meter butterfly in 56.40 seconds; he was defeated by fellow American Doug Russell by a half second, despite holding the world record and having beaten Russell the previous ten times they had swum against each other that year.
At age 41, Spitz attempted a comeback for the 1992 Summer Olympics after film maker Bud Greenspan offered him a million dollars if he succeeded in qualifying.
In 1973–74, Spitz appeared on TV's The Tonight Show Starring Johnny Carson and The Sonny and Cher Comedy Hour. , he portrayed Pete Barlow, who accidentally shoots his wife (played by Spitz's wife, Suzy).
He also appeared briefly on The Dean Martin Celebrity Roast of then-Governor of California Ronald Reagan in September 1973.
In 1966 at age 16, he won the 100-meter butterfly at the AAU national championships, the first of his 24 total AAU titles. The Weinstein JCC in Richmond was one of the Host JCC's for the 2005 games with over 1,000 teenagers participating in various sports, including swimming.
The following year, Mark set his first world record at a small California meet in the 400-meter freestyle with a time of .60, and emerged on the world swimming stage. He won five gold medals at the 1967 Pan American Games, setting a record that lasted until 2007 when Brazilian swimmer, Thiago Pereira, won six golds at the XV Pan American Games in Rio de Janeiro.
Minutes before the race, he confessed on the pool deck to ABC's Donna de Varona, "I know I say I don't want to swim before every event, but this time I'm serious. If I swim seven and win six, I'll be a failure." Spitz won by half a stroke in a world-record time of 51.22 seconds. Spitz's record of seven gold medals in a single Olympics was not surpassed until Phelps broke the record at the 2008 Summer Olympics.