WordNet (r) 3.0 (2006):

sidestroke
    n 1: a swimming stroke in which the arms move forward and
         backward while the legs do a scissors kick

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "sidestroke":
   Australian crawl, aquaplaning, aquatics, backstroke, balneation,
   bathe, bathing, breaststroke, butterfly, crawl, diving, dog paddle,
   fin, fishtail, flapper, flipper, floating, natation, surfboarding,
   surfing, swim, swimming, treading water, wading, waterskiing