Marilyn Corson was the daughter of RoseMary Dawson, a top American swimmer and coach, and the granddaughter of Matt Mann, a coach at the University of Michigan and of the 1952 American Olympic Team, so it was not surprising when she took to the water at a young age. She made her international debut for Canada at the 1966 British Empire and Commonwealth Games, where she took silver in the 220 yard butterfly. Her next stop was the 1967 Pan American Games, where she captured silver in the 4x100 m medley relay and bronze in the 100 and 200 metre butterfly events, as well as the 400 metre individual medley. She was then selected to represent Canada at the 1968 Summer Olympics, where she won bronze in the 4x100 m freestyle relay (alongside Angela Coughlan, Marion Lay, and Elaine Tanner) and was eliminated in the opening round of the 100 and 200 m butterfly events. After the Games she entered Michigan State University and competed on their swim team, but made a final appearance for Canada as captain of the nation’s delegation to the 1972 Summer Olympics. In Munich she finished seventh in the 4x100 m medley relay (with Leslie Cliff, Wendy Cook-Hogg, and Sylvia Dockerill), was eliminated in the semifinals of the 100 m butterfly, and stayed to marry her husband Mike Whitney. She retired from active competition after the Games and was inducted into the Ontario Aquatic Hall of Fame in 1994.
Date of birth is uncertain. Commonwealth Games data also has a DOB of 6 June 1954, but multiple sources confirm the DOB listed above.