The depth of shallow waters, called the photic (“sunlight”) zone, varies depending on conditions. In murky waters of bays near the mouths of rivers, it might extend down to only about forty feet or so; in clear, tropical waters, it can reach down to around six hundred feet. Where there’s light, there’s life. The photic zone is the only place in the ocean where there’s enough light to support photosynthesis. Although it makes up only 2 percent of the entire ocean, it houses around 90 percent of its known life.
