Lake Taal, formerly known as Bombon Lake, is 60 km south of Manila. It is the deepest lake in the Philippines (172 m) and the third largest in area (234.2 km2). It is a caldera lake, having been formed partly by the collapse of a large volcanic crater and partly by subsidence. Subsequent volcanic activity has modified the morphometry of the lake. During the 10th century, it was connected to the sea at Balayan Bay by a wide channel, but an extremely powerful eruption of the Taal Volcano in 1754 rearranged the shape of the lake and narrowed the outlet to form the present day Pansipit River, the lake's only outflow, which leaves the lake in its southwest corner and travels about 10 km to the sea.

A high ridge, part of the crater wall, rises to 640 m above sea level to the northwest of the lake, upon which is located the chief town in the catchment area, Tagatay City. To the south and east, the land is more gently sloping. The region is still volcanically active an island of 4,537 ha in the lake contains a crater lake of about 30 ha formed by an eruption in 1911, and a crater about 2 km away from the crater lake was formed by an eruption in 1967.

There are about 4 species of endemic fish in the lake. The most important is clupeid (Harengula tawilis), which is the basis of an important subsistence fishery. The fish fauna also includes important migratory components composed mainly of mullets (Mugilidae) and jacks (Carangidae) which move up the Pansipit River when juvenile and spend their lives in the lake until they are sexually mature, at which time they return to the sea. These fishes also support valuable fisheries, but the indications are that their numbers have been declining due to over-fishing in the Pansipit River. In addition, there is some floating cage culture of Oreochromis nilotica in sheltered bays.

The catchment area is largely deforested and given over to agriculture. Coconut cultivation is important, with additional crops such as coffee, cocoa and cassava grown underneath the coconut trees. Other areas are dominated by grassland (Imperata cylindrica) and there is some livestock raising.

There is very little industry in the catchment area at present. Major threats to the lake include over-exploitation of fishery resources, inappropriate development for tourism and plans to use the lake water for irrigation and domestic water supply (Q).