The ocean is divided into distinct zones of marine life. which three factors are
used to define the zones?

Three factors are used.

The availability  of sunlight.

The distance from shore and

The  water depth.

Explanation:

Availability of Sunlight

The photic zone is the upper part of the ocean  into which sunlight penetrates.

Distance from Shore

The intertidal zone is the strip of land where the  land and ocean meet and overlap, or the zone  between high and low tides.

The neritic zone is the marine-life zone that  extends from the low-tide line out to the shelf  break.

The oceanic zone is the marine-life zone  beyond the continental shelf.

Water Depth

The pelagic zone is open zone of any depth.  Animals in this zone swim or float freely.

The benthic zone is the marine-life zone that  includes any sea-bottom surface regardless of  its distance from shore.

The abyssal zone is a subdivision of the benthic  zone characterized by extremely high pressures,  low temperatures, low oxygen, few nutrients,  and no sunlight