Named Hon Mun because in the South East of the Island, it has highrise cliffs with dangerous wattles forming caves and grottoes, especially its stones are as black as ebony, which could rarely be found in other areas. In the black-stone caves of Hon Mun, every year flocks of Yen birds migrate to the area and build their nests.

Due to the island's location adjacent to the hot sea-currents from the equator, suitable to the development conditions of corals and various types of tropical sea creatures, the sea bed of Hon Mun is home to an abundant and diverse group of marine species, an interesting and useful place for researchers, oceanographers and tourists to observe and explore more of the sea creatures' life.