At age 16, Leslie Cliff dazzled the international swim scene by winning three gold and two silver medals in one competition at the 1971 Pan American Games. Cliff swam for the Canadian Dolphin Swim Club, coached first by fellow BC Sports Hall of Famer, Howard Firby, and later by another BC Sports Hall of Famer Deryk Snelling. She was the recipient of the Order of Canada in 1972 and the Beatrice Pines Trophy that same year as Canada’s outstanding female swimmer. As well, she was inducted into Canada’s Sports Hall of Fame.

Cliff made her international debut at the 1970 Commonwealth Games where she reached the finals in her events.

Cliff won three gold (200m and 400m individual medley, 4x100m medley relay) and two silver medals (100m butterfly, 4x100m freestyle relay) at the 1971 Pan American Games held in Cali, Colombia.

A year later she was a silver medalist at the 1972 Olympic Games in Munich in the 400m individual medley. She won gold and silver at the 1973 USAAU championships. At the 1974 Commonwealth Games, she was a double-gold medalist in the 200m and 400m individual medleys.

Nationally Cliff won over fifty Canadian medals between 1970-75 and held numerous Canadian senior records.