<P> Taal Lake was once an inlet of nearby Balayan Bay, and was easily navigable from it . A series of major eruptions in the early 18th century battered the lakeside towns with earthquakes and volcanic debris . The activity culminated in 1754 with Taal Volcano's largest eruption that blocked Pansipit River with tephra, blocking the lake's sole outlet to the sea . This caused the waters to rise, eventually submerging several lakeside towns--the remnants of which are reportedly visible underwater to this day . Since the 1754 eruption, the surface elevation had risen from sea level to 5 metres (16 ft) above sea level, with the lake's once saline waters becoming freshwater after centuries of precipitation . </P> <P> The poblaciones (town centres) of Lipa, Taal, Sala, Bauan, and Tanauan were abandoned and reestablished several kilometers away from the lakeshore after volcanic activity had subsided . Over a century hence, newer settlements along the lakeshore were carved from the larger towns: Talisay (established 1869, from Taal), Cuenca (1877, from San José), Alitagtag (1910, from Bauan), Mataasnakahoy (1932, from Lipa), Agoncillo (1949, from Lemery), San Nicolas (1955, over the ruins of old Taal), Laurel (1961, from Talisay), Santa Teresita (1961, from Taal, San Luis, and San Nicolas) and Balete (1969, from Lipa). </P> <P> As the lake was previously connected to the sea, it is home to many endemic species that have evolved and adapted to the desalination of the lake's waters . The lake has a freshwater - adapted population of trevally, Caranx ignobilis . This fish, also found in Pansipit River, is locally called maliputo . Its most popular endemic species is the overharvested Sardinella tawilis, a freshwater sardine . The two other endemic fish species in Taal Lake are the gobies Gnatholepis volcanus and Rhinogobius flavoventris . </P> <P> Taal Lake is also home to one of the world's rarest sea snakes, Hydrophis semperi . This particular species is only one of two "true" sea snake species that are known to live entirely in freshwater (the other is Laticauda crockeri from the Solomon Islands). Bull sharks, Carcharhinus leucas, used to be part of the lake's once - diverse ecosystem but were extirpated by the locals by the 1930s . </P>

An island inside a lake inside an island