Fish began his career in karts at 13. He then moved to Formula Ford in 1979 at age 18 and then British Formula Three. He then came to the United States and competed in various classes of SCCA competition as well as IMSA GT. He was the 1987 Formula Atlantic champion and then made 14 starts in the Indy Lights series. He returned to sports cars. He was the GTO class winner at the 12 Hours of Sebring and 24 Hours of Daytona in 1990.
Calvin is featured in all editions of the Ayrton Senna story.[clarification needed] Fish and Senna were fierce rivals in the junior formulae in the UK. Both had the utmost respect for each other, hence, the acknowledgement of Fish in any of the books written about Senna. Fish is one of the few drivers to beat Senna in F3 and F2000.