Sunlight entering the water can travel as much as 3,000 feet into the ocean depths under the right conditions, but ordinarily there is no significant light that penetrates beyond about 650 feet down. That upper 650 feet is called the euphotic or “sunlight” zone and is home to most familiar marine life. The “dark ocean”, everything below that depth, makes up 90% of the ocean and remarkably little is known about it.
