Debbie Clarke took up swimming in the late 1960s. Her only major international appearance for Canada was the 1976 Summer Olympics, where she was an alternate on the 4x100 metre freestyle and medley relays squads, both of which won bronze. In the former she swam in the opening round alongside Gail Amundrud, Barbara Clark, and Anne Jardin, but was replaced by Becky Smith in the final. In the latter, she helped Wendy Cook-Hogg, Robin Corsiglia, and Susan Sloan reach the final, but was replaced by Jardin in the medal round. She also competed in the 200 metre freestyle event, but was eliminated in the qualifiers. She later attended Northeastern University in Boston and was a member of their swim team, captaining it for three years prior to her 1981 graduation. Following her competitive swimming career she continuedd in the sport as an Assistant Coach with the Thunder Bay Thunderbolts in the early 1980s.