Laguna de Bay is the largest lake in the Philippines and the third largest freshwater lake in Southeast Asia (in terms of surface area) after Tonle Sap in Cambodia and Lake Toba in Sumatra, Indonesia. It is located in the island of Luzon between the provinces of Laguna to the south and Rizal to the north. Metro Manila lies on its western shore. Its surface area is 949 square kilometers and has an average depth of only about 2 meters. The lake is shaped like a stylised 'W', with two peninsulas jutting out from the northern shore. Between these peninsulas, the middle lobe fills a large volcanic caldera. Laguna de Bay drains to Manila Bay via the Pasig River. The lake is filled with fish pens installed by fishermen who regularly fish there.

There is a large island in the lake, Talim Island, which is under the jurisdiction of the towns of Binangonan and Cardona in Rizal province.

Currently, the lake serves as a multipurpose resource. It is a navigational lane for passenger boats, source of water for a nearby hydroelectric power plant, food support for the growing duck industry, aquaculture, recreation, fishery, flood control, source of irrigation water and a "virtual" cistern for domestic, agricultural and industrial effluents (Gonzales, 1987). Because of its importance in the development of the Laguna de Bay Region , unlike in other lakes in the country, its water quality and general condition are closely monitored (Department of Environment and Natural Resources, 1996). This important water resource has been greatly affected by development pressures like population growth, rapid industrialization, and resources allocation (Batu, 1996).

Government data showed that about sixty percent of the estimated 8.4 million people residing in the Laguna de Bay Region discharge their solid and liquid wastes indirectly to the lake through its tributaries. A large percentage of these wastes are mainly agricultural while the rest are either domestic or industrial (DENR, 1997). According to DENR (1997), domestic and industrial wastes contribute almost equally at thirty percent each. Meanwhile, agricultural wastes take up the remaining forty percent. In a recent sensitivity waste load model ran by the Laguna Lake Development Authority's (LLDA) Integrated Water Resources Management (IWRM) Division, it revealed that 70 percent of Biochemical Oxygen Demand (BOD) loadings came from households, 19 percent from industries, and 11 percent came from land run-off or erosion (LLDA, 2005).

As far as industries and factories are concerned, there are about 1,481 and is expected to increase over time (Guerrero & Calpe, 1998). Of the said figure, about 695 have wastewater treatment facilities. Despite this, the lake is absorbing huge amounts of pollution from these industries in the forms of discharges of industrial cooling water, toxic spills from barges and transport operations and hazardous chemicals like lead, mercury, aluminum and cyanide (Sly, 1984). Based from the said figure, sixty five percent are classified as "pollutive" industries.

The hastened agricultural modernization throughout the region took its toll on the lake. This paved the way for massive and intensified use of chemical based fertilizers and pesticides whose residues eventually find their way to the lake basin. These chemicals induce rapid algal growth in the area that depleted oxygen levels in the water. Hence, oxygen available to the lake is being used up thereby depleting the lake of available oxygen for the fish causing massive fish kills (Solidarity for People's Power, 1992). As far as domestic wastes are concerned, around ten percent of the 4,100 metric tons of waste generated by residents of Metro Manila are dumped into the lake. As reported by the now defunct Metropolitan Manila Waterworks and Sewerage System (MWSS), only 15 percent of the residents in the area have an effective waste disposal system. Moreover, around 85 percent of the families living along the shoreline do not have toilets (SPP, 1992; Batu, 1996).