aquarobics
From Longman Dictionary of Contemporary Englishaquarobicsaq‧ua‧ro‧bics /ˌækwəˈrəʊbɪks $ -ˈroʊ-/ noun [uncountable] aerobics (=very active physical exercise done to music, usually in a class) that you do in a swimming poolAquarobics is followed by a singular verb: Aquarobics is surprisingly effective exercise.