Laguna de Bay (Lake Bay) is often erroneously called the "Laguna Lake". It is the largest lake in the Philippines. On the lake, there are an island, Talim, and two peninsulas jutting out a long way from the north coast. The lake is considered to have once been a branch of Manila Bay but later became separated from the bay by volcanic deposits and the upheaval of land. Water flows out from the northwestern end of the lake to Manila Bay. Since the difference of water level between the lake and the sea is so small, the adverse tides occur frequently during the dry season from January to April.

Vast paddy fields, sugar cane fields and coconut plantations spread over the alluvial plain around the lake. Cash products like vegetables, fruits and poultry are also raised for consumption in neighboring big cities as Manila and Quezon City. The Laguna Lake Development Authority established in 1970 is mainly responsible for promoting development and conservation works in the lake and its drainage basin (Q1).