Lembeh Strait is a name synonymous with "critter" or "muck" diving. Consistently rated among the top dive locations in the world, Lembeh is home to many unique and rare "critters" - a term coined to describe those small creatures that dwell in primarily black sand environments. The factors that contribute to Lembeh having such a high concentration of these unique animals are described below.

Lembeh Island is located at the northeastern most tip of Sulawesi. Lembeh Strait is the body of water separating Lembeh Island from mainland North Sulawesi. During the pleistocene period, this area became isolated, resulting in a very high level of "speciation", i.e. the development of new species.

Located within the epicenter of the coral triangle, which represents the area of earth with the highest numbers of species, North Sulawesi is known for its exceptional variety of terrestrial and underwater life. Sulawesi straddles both the Asian and the Australian biogeographical zones, hosting the highest number of coral, plant and fish species on earth. There are at least 450 species of hard coral in this small area, compared to the 60 species found in the entire Caribbean.

Furthermore, a 30 cm difference between the water levels of the Pacific and Indian Oceans causes a large amounts of nutrient-rich water to flow through the Strait at every tidal change. Nutrients from these tidal flows are retained in the Strait by the actions of small eddies, slow water whirls, created by the narrowness of the passage and the fast changing water flows.

The Strait itself is a narrow channel, only 14 km long and 1-2 km wide. While the general diversity of the area is caused by the unique geographic position of the Strait, its particular diversity is then greatly influenced by the vast array of different underwater habitats present in Lembeh. There are black volcanic sand slopes (TK Bbay, Rojos, etc.), white limestone sandy slopes (Pante Parigi, Tanjung Tebal, etc.), ship wrecks (Kapal Indah, Mawali), pinnacles (Batu Kapal) , zones of rubble patches (Police Pier, Bronsel, etc.) and and rocky reefs with colourful soft coral gardens (Nudi Retreat, Nudi Falls, Angels Window, Batu Sandar, etc.). In addition,the southern and the northern entrances to the Strait are rimmed by rich coral reefs and there are unique shallows along the Strait’s coast lines (Dante’s Wall, Pulau Putus, Batu Angus, California Dreaming, Goby a Crab, etc.).

Each particular habitat supports a different set of marine organisms. There are dive sites where we find the famous cephalopods of Lembeh: the mimic, wonderpus, mototi and hairy octopus and flamboyant cuttlefish, just to mention a few. Then there are the seahorse species; in addition to the four pygmy species found to date in Lembeh, there are the estuary, common, and thorny seahorses. When you ask our dive guides to show you a frogfish, they answer with a question: How many and what kind would you like to see? Almost all types are represented: warty, hairy, painted and giant to name a few. There are hundreds of nudibranch and crustacean species. The list of species represented from the Scorpionidae family just goes on and on: cockatoo wasp fish, devil fish, short spine lionfish, ambon scorpionfish, rhinopias, etc.

There is nowhere else in the world, where visitors can find such an extensive array of marine life and underwater topographical features in such close proximity.