Greetje Galliard began her sporting career during the war, becoming a champion swimmer in the Netherlands. Galliard specialised in the 100 metres backstroke, winning the Dutch title in the event for three consecutive years from 1946 to 1948. In 1947 the first post-war European swimming championships were held in Monte Carlo, where she just missed out on a medal after finishing fourth. One year later she was selected to represent the Netherlands at the 1948 London Olympics, where she placed eighth in the final. Galliard returned to the European Championships in 1950, this time winning bronze. At the end of the year, she travelled to Australia and New Zealand with fellow swimmer Irma Schuhmacher on a three-month competition tour, with Schuhmacher eventually emigrating to Queensland, whereas Galliard returned to the Netherlands.