Coelacanth

Encountering a coelacanth is strictly outside the limits of recreational scuba diving, as their daytime habitats generally begin well below 90 to 100 metres. Only highly experienced, certified trimix and rebreather divers operating within dedicated scientific or exploratory expeditions should attempt such descents. Divers must maintain pristine buoyancy and execute slow, deliberate fin kicks to avoid disturbing delicate cave sediments, which can instantly reduce visibility to zero in confined caverns. Coelacanths possess extremely sensitive eyes adapted to deep twilight; therefore, powerful video lights and strobes must be kept to low intensities or fitted with red filters to avoid blinding the animal or causing undue stress. A non-intrusive approach is essential—divers should remain stationary, allow the fish to dictate the encounter, and maintain a respectful buffer distance.

Encounters with wild coelacanths are exceedingly rare and generally restricted to technical mixed-gas divers or submersibles. In South Africa, specifically the deep submarine canyons of Sodwana Bay within the iSimangaliso Wetland Park, expeditions have recorded sightings in depths between 100 and 120 metres. Here, calmer sea conditions are typically found during the winter months from May to August, which offer the best operational windows for deep technical dive teams. In the volcanic waters of the Comoros Islands (notably Grande Comore), sightings occur along steep lava drop-offs, with relatively stable diving conditions from September to November. In Indonesia, around North Sulawesi near Manado and Bunaken, deep surveys occasionally document the Indonesian coelacanth, with the dry season from April to October presenting the most favourable surface and underwater conditions for deep offshore expeditions.

The coelacanth is a bathydemersal marine species that inhabits deep volcanic reef drop-offs, submarine caves, and rocky canyons, typically at depths between 100 and 500 metres where water temperatures remain between 15°C and 22°C. They rely heavily on geologically complex underwater terrain, using rugged basalt caverns and overhangs during the day as thermal and current refuges before moving into open bathyal waters at night. The waters this animal calls home are primarily centered in the Western Indian Ocean, with established populations documented off the Comoros, Tanzania, Kenya, Mozambique, Madagascar, and the deep underwater canyons of Sodwana Bay in South Africa. A second recognised species resides in deep waters off North Sulawesi and Papua in Indonesia.

Coelacanths are opportunistic, benthic drift feeders that hunt primarily under the cover of darkness along steep submarine canyons and boulder slopes. Moving slowly above the seabed, they conserve metabolic energy by drifting with local currents. To locate prey hidden in crevices or buried in sediment, they utilise their specialised rostral organ—a gel-filled cavity in the snout that senses minute electrical impulses generated by moving animals. When prey is detected, the coelacanth executes a swift lunging strike, using its intracranial joint to flex its skull open wide and create intense suction. Their diet consists predominantly of deep-water benthic and epibenthic teleosts, such as cutlassfish, lanternfish, cardinalfish, and deep-sea eels, as well as squids, octopuses, and small benthic sharks. Digestion occurs slowly due to their remarkably low metabolic rate.