Manila Bay is a natural harbour which serves the Port of Manila (on Luzon), in the Philippines. Strategically located around the capital city of the Philippines, Manila Bay facilitated commerce and trade between the Philippines and its neighbouring countries, becoming the gateway for socio-economic development even prior to Spanish occupation. With an area of , and a coastline of , Manila Bay is situated in the western part of Luzon and is bounded by Cavite and Metro Manila on the east, Bulacan and Pampanga on the north, and Bataan on the west and northwest. Manila Bay drains approximately of watershed area, with the Pampanga River contributing about 49% of the freshwater influx. With an average depth of , it is estimated to have a total volume of 28.9 billion cubic metres (28.9 cubic km). Entrance to the bay is wide and expands to a width of . However, width of the bay varies from at its mouth and expanding to at its widest point.