The document describes the three zones of the ocean: the sunlight zone from the surface down to 600 feet where 90% of marine life lives due to sufficient light for photosynthesis; the twilight zone from 600 to 3,000 feet with some light penetration where organisms have adapted to low light conditions; and the midnight zone below 3,000 feet that is entirely dark, near freezing temperatures, and home to bacteria that use minerals from cracks in the earth's crust as an energy source to nourish other living things in the zone.