The province owes its name to this body of water that forms its northern boundary which, in turn, was named after the first provincial capital, the town of Bay.
Laguna de Bay is Southeast Asia’s third largest fresh water lake. It stays pristine throughout the year as the area is blessed with regular rain showers.
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.