Margaret Isobel Lister (née Sweeney, born 1929 or 1930) is a former New Zealand swimmer who represented her country at the 1950 Empire Games in Auckland.
[2] She went on to represent New Zealand at the 1950 British Empire Games in Auckland, finishing sixth in the 220 yards breaststroke with a time of 3:28.0.
[3] She was also a member of the New Zealand team in the 330 yards medley relay, with Jean Stewart and Winifred Griffin, that was disqualified in the final.
[5] On 30 January 1955, she became the first person to swim the length of Lake Taupo, making the 40-kilometre (25 mi) crossing from south to north in 13 hours 39 minutes.
[8] In 1955, she was within 800 yards (730 m) of reaching the English coast when the tide changed and pushed her back; she finally abandoned the attempt after 12 hours in the water.