This small passage between the islands of Gili Lawa Laut and Gili Lawa Darat in North Komodo is so complex and diverse it has two names! North Passage describes its geography, but for any who have experienced these churning waters on a fast tide, The Cauldron is definitely more apt. Best attempted on a falling tide, the dive starts on a reef wall that drops down to 25 m with scattered coral bommies on the sandy ocean floor. As you slowly drift with the current into the passage, the bottom becomes more rocky, with stunning coral bommies covered in branching gorgonian fans, table corals and stands of Acropora, engulfed by clouds of glass fish. The bottom gradually shallows to 14 m, before suddenly dropping to 22 m as you enter The Cauldron—a large depression about 30 m across carved out of the centre of the passage. On the right is a stunning soft coral wall, with caves and crevices near the surface that are worth exploring. On the opposite side are a couple of canyons where you can shelter from the current while admiring the beautiful hard coral formations and dense schools of midnight snapper, big eye trevally, sweetlips and giant trevally. Mantas are occasionally seen here, somersaulting gracefully as they feed in the current. There are a number of ways to dive this site depending on your experience and the conditions. Photographers will prefer to stay near the entrance and to dive at slack or on a gentle fall. Finish the dive amongst the shallow coral bommies littered across the sandy bottom to the northern side of the passage. Other more adventurous divers can attempt this site during a strong current, and let it carry you across The Cauldron and up through the canyon, much to the dislike of your dive computers. The current will carry you through the canyon at high speed and, once clear, you can drop back down to about 12 m and drift gently with the current for a few minutes through schools of fusiliers. Head left to swim out of the main current flow and into a back eddy that will gently carry you up onto the reef near Gili Lawa Laut for a safety stop amongst a vibrant coral garden. This is an exhilarating dive when approached carefully. Be sure to follow your guide’s instructions to avoid becoming separated form the group in these strong currents. Once in the current, you have no choice but to go with the flow. The rocks are covered in barnacles, and if you try to hold on to wait for the group, your fingers will be the first casualties!
The whitetip reef shark (Triaenodon obesus) is a species of requiem shark, family Carcharhinidae, and the only member of its genus. A small shark usually not exceeding 1.6 m (5.2 ft) in length, this species is easily recognizable by its slender body and short but broad head, as well as tubular skin flaps beside the nostrils, oval eyes with vertical pupils, and white-tipped dorsal and caudal fins. One of the most common sharks found on Indo-Pacific coral reefs, the whitetip reef shark occurs as far west as South Africa and as far east as Central America. It is typically found on or near the bottom in clear water, at a depth of 8–40 m (26–131 ft). During the day, whitetip reef sharks spend much of their time resting inside caves. Unlike other requiem sharks, which rely on ram ventilation and must constantly swim to breathe, this shark can pump water over its gills and lie still on the bottom. At night, whitetip reef sharks emerge to hunt bony fishes, crustaceans, and octopus in groups, their elongate bodies allowing them to force their way into crevices and holes to extract hidden prey. Individuals may stay within a particular area of the reef for months to years, time and again returning to the same shelter. This species is viviparous, in which the developing embryos are sustained by a placental connection to their mother. One of the few sharks in which mating has been observed in the wild, receptive female whitetip reef sharks are followed by prospective males, which attempt to grasp her pectoral fin and maneuver the two of them into positions suitable for copulation. Females give birth to one to six pups every other year, after a gestation period of 10–13 months. Whitetip reef sharks are rarely aggressive towards humans, though they may investigate swimmers closely. However, spear fishers are at risk of being bitten by one attempting to steal their catch. This species is caught for food, though ciguatera poisoning resulting from its consumption has been reported. The IUCN has assessed the whitetip reef shark as Near Threatened, noting its numbers are dwindling due to increasing levels of unregulated fishing activity across its range. The slow reproductive rate and limited habitat preferences of this species renders its populations vulnerable to overfishing.
Bleaching occurs when corals expel their symbiotic zooxanthellae - pigmented, algae-like protozoa that live within the coral's cells. High temperature, pollution or other stresses can cause the coral to expel its zooxanthellae, leading to a lighter or complete loss of color.