Panglao is an island in the Philippines located in the Central Visayas, it is a popular tourist destination in the Philippines and includes several small islands like Gak-ang, Pontod, and Balicasag. Panglao has a terrain that range from plain, hilly to mountainous. Panglao is made of Maribojoc Limestone, the youngest of the limestone units found in the western area of Bohol. The limestone composition halted the development of an airport as coralline limestone is soluble which causes formation of caves and sinkholes. One interesting geological feature found in the island is the Hinagdanan Cave which has an underground water source.
The cave is an important water source as the island has no rivers or lakes. About 250 new species of crustaceans and 2500 new species of mollusks were found around the island. The discovery was the work of the Panglao Marine Biodiversity Project. The project found that Panglao alone has more marine biodiversity than Japan and the Mediterranean sea.