Eastern Kalimantan, on the Indonesian side of Borneo, is home to some of Indonesia’s least-crowded diving destinations. Centered around the Derawan Archipelago—including the islands of Maratua, Sangalaki, Kakaban, and Derawan—the region lies within the Coral Triangle. Divers can explore coral reefs, dramatic walls, drift dives, lagoons, and the stingless jellyfish lake of Kakaban.

The waters are known for encounters with manta rays, whale sharks, sea turtles, reef sharks, barracuda schools, and a good variety of macro life.

One of the region’s highlights is the opportunity to see the endangered leopard shark, which remains relatively common around several reefs and sandy-bottom habitats in Eastern Kalimantan. These beautifully patterned sharks are often spotted resting on the seabed during the day, making the area one of Indonesia’s best destinations for observing the species in the wild.

Divers may also encounter thresher sharks, whose distinctive elongated tails and graceful movements make them one of the ocean’s most sought-after shark sightings.

Divers should be aware that visibility along parts of the mainland coast can be affected by sediment-rich runoff from the massive river systems that drain the interior of Kalimantan. These rivers carry large volumes of freshwater and suspended sediment into the sea, often reducing underwater visibility for up to 30 kilometres offshore. As a result, the region’s premier dive sites are generally located around offshore islands and reefs, where clearer oceanic waters provide better visibility and healthy coral ecosystems.

Because of the influence of river runoff, tidal conditions play an important role in dive planning. Local dive operators carefully time dives to coincide with favourable tidal phases, which can bring in clearer oceanic water and significantly improve underwater visibility. Understanding the tides is therefore essential not only for safety and current management, but also for experiencing the best possible conditions at many of the region’s dive sites.