Final answer:
The surface portion of a body of water where photosynthetic activity is possible, up to the maximum depth at which sunlight can penetrate, is called the photic zone.
Step-by-step explanation:
The surface portion of a body of water where photosynthetic activity is possible, up to the maximum depth at which sunlight can penetrate, is called the photic zone. This zone receives enough sunlight to support photosynthesis, allowing algae and other photosynthetic organisms to produce food and support food webs. It extends up to a maximum depth of 200 meters (656 feet) below the water's surface.