The Bay is approximately 8 mi (12.8 km) long and 2.7 mi (4.3 km) broad, with a mouth opening of about 4.6 mi (7.4 km) and maximum depth of 40 ft (12 m). Unique features include the only significant barrier reef in the main Hawaiian Islands and extensive development within a large lagoon of shoaling reefs. Two navigable channels cut across the northern and southern ends of the barrier reef. The deeper, northern channel, located off Kualoa Beach Park, provides entrance from the North Pacific Ocean to a ship channel dredged the length of the lagoon between 1939 and 1945. The lagoon contains extensive patch and fringing reefs and its southern end is partly enclosed by the Mokapu Peninsula. This peninsula is occupied by Marine Corps Base Hawaii.
A sand bar (Ahu o Laka or locally, the sand bar), Kapapa, and Kekepa (Turtleback Rock) are exposed features on the barrier reef.
Two islands within Kāne'ohe Bay are prominent: Mokoli'i (Chinaman's Hat) and Moku o Lo'e (Coconut Island).
The largest of these five islets or islands is Coconut Island, an isolated volcanic remnant located in the southwest
part of the bay. Coconut Island is owned by the State of Hawaii and home to the University of Hawaii, Hawaii Institute
of Marine Biology (HIMB) and Pauley-Pagen Laboratory (SOEST). Coconut Island was immortalized in the beginning sequence to the television program Gilligan's Island.