Marianne Yvonne Heemskerk (born 28 August 1944 in Rotterdam, South Holland) is a former butterfly swimmer from the Netherlands, who won the silver medal in the 100 m butterfly at the 1960 Summer Olympics in Rome, Italy. She was also part of the 4 × 100 m medley relay team that finished fourth. She also participated in the 1964 Summer Olympics but did not reach the finals. Heemskerk broke the world record in the women's 200m butterfly on 12 June 1960 in Leipzig, East Germany. References 1944 births Living people Olympic swimmers of the Netherlands Dutch female butterfly swimmers Swimmers at the 1960 Summer Olympics Swimmers at the 1964 Summer Olympics Olympic silver medalists for the Netherlands Swimmers from Rotterdam World record setters in swimming European Aquatics Championships medalists in swimming Medalists at the 1960 Summer Olympics Olympic silver medalists in swimming 20th-century Dutch women