John Siman played water polo for the US at the 1984 Los Angeles Olympics. He also made the ill-fated 1980 US Olympic team that could not compete at the Moskva Olympics. Siman was a member of the gold medal winning team at the 1983 Pan American Games, and played at the 1978 and 1982 World Championships. He attended Cal State Fullerton, graduating in 1975. Siman played on national championships teams in 1981-82 and was named All-American in 1980-83. He was the oldest player on the US water polo team at the 1984 Olympics.