 The tawny nurse shark may be one of the few fishes specializing in preying on <unk> . Other known food items include <unk> , sea <unk> , crustaceans ( e.g. crabs and lobsters ) , <unk> , small fishes ( e.g. <unk> , <unk> , and <unk> ) , and the occasional sea snake . Hunting tawny nurse sharks swim slowly just above the sea floor , poking their heads into depressions and holes . When a prey item is found , the shark <unk> expands its large , muscular <unk> , creating a powerful negative pressure that sucks the prey into its mouth . 
