Many marine biologists believe that flying fish fly mostly to avoid being chased by large fish such as tuna and swordfish, or because ships are frightened when they approach. The big family of marine fish is not always calm. Flying fish are small and medium-sized fish living in the upper ocean, and they are the targets of fierce fish such as sharks, flowers, tuna and swordfish. Flying fish don't jump out of the water easily. Only when they are attacked by enemies or stimulated by the vibration of ship engines can they display this skill. But sometimes, flying fish will jump out of the water due to excitement or reproduction, and sometimes flying fish will take off for no reason. Flying fish's eyesight is very weak, and it can hardly be seen at night. Flying fish has phototaxis, so flying fish often becomes a "free lunch" on the deck of ships.