The Indian Ocean is the third largest of the world’s oceans. It lays between Africa, Antarctica, Asia and Australia and is unique in the fact that most of its water is below the equator.  It is closed on the Northern end by the Asian land mass. It covers an area of 73.6 million square kilometers, including the Arabian Sea, Bass Straight, Bay of Bengal, Great Australian Bight, Gulf of Oman, Persian Gulf, Red Sea, Straight of Malacca and other tributary bodies of water. The area of the Indian Ocean is just short of 8 times the size of the United States. Its coastline runs for 66,526 kilometers.

The Mid-Indian Ocean Ridge dominates the floor of the Indian Ocean. It is subdivided by the Southeast Indian Ocean Ridge, the Southwest Indian Ocean Ridge and the Ninety East Ridge, which is very straight and lies along the 90^th eastern parallel. Its lowest point is the Java Trench, 7,258 meters below sea level. Two types of topography dominate – smooth (abyssal plains) near the continents where the sediment spreads out and rough/uneven (abyssal hills) areas in the central part of the ocean.

Ocean currents vary depending on the hemisphere. In the southern Indian Ocean, counterclockwise gyre (broad, circular systems of currents) dominate, while the direction of the currents switches in the Northern Hemisphere, a feature unique to the Indian Ocean.

Two major weather features can be observed in the region of the Indian Ocean: monsoons and cyclones. Monsoons, winds that change direction with seasonal change, are common. Northeast monsoons happen in December through April and are also paired with northeast to southwest winds and currents caused by high pressure areas over northern Asia due to cold, falling, winter air. Southwestern monsoons occur June through August. These come from southwest to northeast winds and currents from low atmospheric pressure over southwestern Asia caused by hot, rising, summer air. Tropical cyclones occur in the northern Indian Ocean in May/June and October/November and in January and February in the southern Indian Ocean.

The Indian Ocean has many economic uses. It contains many oil and gas fields, including 40% of the world’s offshore oil production. It contains fish and shrimp, sand and gravel aggregates which include beach sands rich in heavy metals, placer deposits, and polymetallic nodules. It is a major sea route since it connects the Middle East, Africa, and East Asia with Europe and the Americas. However, ships traveling in the far southern regions of the ocean near Antarctica can suffer from superstructure icing from May to October.

The Indian Ocean is home to many endangered species including dugong, seals, turtles and whales. There is also oil pollution in the Arabian Sea, the Persian Gulf, and the Red Sea, which are tributaries to the Indian Ocean.