What is the largest and most significant lake in the Philippines?

Laguna de Bay, also known as Laguna Lake, is the largest lake in the Philippines. It is located southeast of Metro Manila, between the provinces of Laguna to the south and Rizal to the north. A freshwater lake, it has a surface area of 911–949 km² (352-366 sq mi), with an average depth of about 2.8 meters (9ft 2in) and an elevation of about one meter above sea level. The lake is shaped like a crow's foot, with two peninsulas jutting out from the northern shore and filling the large volcanic Laguna Caldera.

Laguna de Bay means "Lagoon of (the town of) Bay" for the lakeshore of Bay, the former capital of Laguna province. Alternate spellings of the town's name include "Bae" or "Ba-i", and in the early colonial times, "Bayi" or "Vahi". The Spanish word 'Laguna' refers to not just lagoons but also freshwater lakes, aside from 'lago'. This would make the lake's alternate name, "Laguna Lake", tautological. The lake is a multipurpose resource, used for fishery, transportation, irrigation of agricultural lands, power generation, and as a reservoir for regional flood management, among other things.