Nel Garritsen enjoyed a brief swimming career. A breaststroke swimmer at first, she reached the final of the Olympic 200 m in Helsinki 1952. She placed last in a race that was won using the butterfly technique, and she switched to that stroke. Having already set the first Dutch record in that stroke in 1951, she contested her second international final in 1954, placing 7th in the 100m butterfly at the European Championships in Torino, Italy. In 1953 and 1954, Garritsen won the first two Dutch titles in that same event, representing Rotterdam club RDZ.