submarine, pigboat, sub, U-boat
['modem', 'bathtub, bathing tub, bath, tub', 'crayfish, crawfish, crawdad, crawdaddy', 'gar, garfish, garpike, billfish, Lepisosteus osseus', 'pole', 'steam locomotive', 'hippopotamus, hippo, river horse, Hippopotamus amphibius']