In addition, the green turtles 'eyes have evolved to clearly perceive objects through the medium of water, not the atmosphere above ground. Once they get ashore, they become extremely nearsighted. They have no teeth, and unlike terrestrial turtles, they cannot retract into their shells when faced with danger. These sea turtles therefore lack not only the ability to attack but also a defensive capacity.
此外，由於陸地空氣介質傳導不如海水，海龜上了岸，成為大近視眼，沒有牙齒，又無法像陸龜，遇到危險可以縮頭，因此海龜不僅缺乏攻擊能力，也缺乏防禦力，又為何要冒險上岸？