It is the remains of one of the seven Pleistocene epoch volcanoes that formed the prehistoric Maui Nui island, during the Quaternary Period of the Cenozoic Era.

Its crescent shape protects divers inside it from waves and the channel's powerful currents, though diving also takes place off the 300-foot (91.5-meter) sheer outer wall.

[6] Archaeological evidence, primarily in the form of stone sinkers and lures, show that early Hawaiians visited Molokini to fish.

[7] During World War II, the United States Navy used Molokini for target practice, as its shape is somewhat similar to a battleship.

[8] In 1975 and 1984, the Navy detonated in-place unexploded munitions found within the crater, resulting in the destruction of large areas of coral.

[10] In 1977 Molokini islet, the crater, and the surrounding 77 acres (31 ha) of underwater terrain were declared a Marine Life Conservation District (MLCD).

[citation needed] Most commonly observed among these are the black triggerfish, yellow tang, Moorish idol, parrotfish, raccoon butterflyfish and bluefin trevally.

Due to constant exposure to park visitors and the long history as a conservation district, the fish of Molokini are comfortable with the presence of nearby divers.

[citation needed] Small whitetip reef sharks and moray eels are occasionally seen in the crater, and red pencil urchins can be seen quite frequently.

Visibility at Molokini regularly exceeds 50 feet (15 meters), and the inside of the crater is generally sheltered from strong winds and waves.