Bunaken Island and the four other islands of Siladen, Manado Tua, Montehage and Nain are part of a marine park called Bunaken Marine Park. The total area of the park is 89,065 ha of land (3%) and sea (97%), located in Manado and includes parts of the coastal area of North Sulawesi mainland. The Bunaken National Marine Park was formally established in 1991 and was among the first of Indonesia's growing system of marine parks. It comprises the 5 islands of Bunaken, Manado Tua, Siladen, Montehage and Nain. It is part of the Indo-Pacific region which supports the highest marine biodiversity on earth.

The waters of Bunaken National Marine Park are extremely deep (1566 m in Manado Bay), clear (up to 35-40 m visibility), refreshing in temperature (27-29 C) and harbor some of the highest levels of biodiversity in the world. Pick any of group of interest - corals, fish, echinoderms or sponges - and the number of families, genera or species is bound to be astonishingly high. For example, 7 of the 8 species of giant clams that occur in the world, occur in Bunaken. The park has around 70 genera of corals; compare this to a mere 10 in Hawaii. Although the exact number of fish species is unknown, it may be slightly higher than in the Philippines, where nearly 70% of all fish species known to the Indo-western Pacific, are found.

Some fact include:

• The park is 16,000 sq. km of water and land.

• Water temperature rarely drops below 28 celsius, and averages 29 celsius over the year.

• The dry season is from April to November when the wind blows from south-east and the sea stays relatively calm.

• The wet season is from December to March with cooler winds from north-west which can bring heavier rains and rougher seas.

• Temperatures vary between 25 celsius in the wet season to 30 celsius in the dry season.

• Diving can be undertaken all year round - visibility varies from 30m during the dry season to 15m in the wet season.

• There are 7,000 species of coral fish in the world and over 2,000 can be found in the park.

• Protected fishes that can be found in the area include the coelacanth, turtles, dugongs and giant clams.

• Unusual fish include the pygmy seahorse, the ghost pipefish, frogfish and the blue-ringed octopus.