HSAS GM

Too much sunlight can damage the algae that live inside coral in shallow water. To protect the algae, which are a main source of sustenance for the coral, the corals fluoresce. This creates proteins that act as a sort of sunscreen for the algae.

In these deepest parts of the ocean, the water temperature may only be 2º to 4º Celsius, with the exception of water coming out of hydrothermal vents in the seafloor. The water released from these vents can be up to 400º Celsius (750º Fahrenheit). It's the intense pressure at these depths—the same pressure that would crush you—that keeps the water from boiling.

Oceans have an average depth of 12,100 feet, and because light waves can only pe*****te 330 feet of water, everything below that point is dark. Seeing as water makes up most of the planet, this means that most of Earth exists in absolute darkness all the time.