submarine, pigboat, sub, U-boat
['knot', 'loudspeaker, speaker, speaker unit, loudspeaker system, speaker system', 'chiton, coat-of-mail shell, sea cradle, polyplacophore', 'jellyfish', 'loggerhead, loggerhead turtle, Caretta caretta', 'water snake', 'bannister, banister, balustrade, balusters, handrail']