Answer: paramecium

AnswerCrossword Clue
PARAMECIUMKind of protozoan
PARAMECIUMIt's something in the water
parameciuma genus of tiny animals including the slipper animalcule also PARAMAECIUM, PARAMOECIUM
parameciumA single-celled freshwater animal that has a characteristic slipperlike shape and is covered with cilia