Belongas Bay: Hammerhead Shark Diving in South Lombok

Most people come to Lombok for warm water. They imagine tropical turquoise, bathtub temperatures, and the gentle drift of a coral reef snorkel. Belongas Bay offers something different: cold water surging up from the deep ocean, currents that push and pull with muscular force, visibility that ranges from crystal to murk in the space of a few meters, and the reason you accept all of these discomforts — hammerhead sharks. Schools of them. Swimming in formation along the deep walls of the bay, their unmistakable silhouettes — flattened heads, swept-back profiles — appearing from the blue like something from a nature documentary, except you are in the water with them.

Belongas Bay is not a dive destination for everyone. It is not a coral garden to be drifted over in warm, calm water. It is a serious dive site with serious conditions, and it demands serious skills from the divers who want to experience its rewards. The hammerheads are the headliners, but the supporting cast — mantas, mobula rays, tuna, barracuda, and the occasional mola mola — would make any diver's trip even without the sharks.

Belongas Bay opens onto the Indian Ocean on Lombok's south coast, roughly 25 km southwest of Kuta. The bay is wide and deep, with underwater topography that creates the conditions for spectacular marine encounters: deep walls drop from 10 meters to beyond 40 meters, underwater pinnacles rise from the depths creating current eddies where fish congregate, and cleaning stations on the wall faces attract sharks and rays that come to have parasites removed by small cleaner wrasse.

The bay's position on the south coast, exposed to the full force of the Indian Ocean and the deep-water upwelling driven by the southeast trade winds, is the key to its marine richness. During the dry season (June-October), cold, nutrient-rich water from deep ocean layers rises to the surface in the bay, driven by wind and current patterns. This upwelling brings nutrients that feed plankton, which feeds small fish, which attracts large predators. The hammerhead sharks follow this food chain to Belongas, aggregating at the bay's cleaning stations and wall edges during peak upwelling months.

The same upwelling that attracts the sharks creates the diving challenges. Water temperatures at depth can plummet from a comfortable 28 degrees to a bone-chilling 18 degrees across a thermocline layer that you swim through in seconds. The cold hits like a wall — your exposed skin contracts, your breathing rate increases, and your body starts burning calories faster to maintain core temperature. Without a thick wetsuit (5mm minimum, 7mm recommended by some operators), the cold becomes debilitating within minutes.

### The Magnet

Belongas Bay's signature dive site, named for its magnetic attraction to marine life. The Magnet is an underwater pinnacle that rises from 35 meters to about 12 meters below the surface, creating a current shadow where fish aggregate and sharks patrol. The dive typically involves a negative entry (jumping in and descending immediately rather than swimming on the surface), a rapid descent to 25-30 meters, and a gradual ascent along the pinnacle face as the dive progresses and air is consumed.

At depth, the hammerheads appear. They cruise the edges of the pinnacle, swimming in loose formations that can number 20, 30, or more individuals. The sharks are typically 2-3 meters long — large enough to be impressive, small enough to be more beautiful than intimidating. They swim with the effortless efficiency of animals perfectly adapted to their environment, each stroke of the cephalofoil (the hammer-shaped head) serving as both steering mechanism and electroreceptive antenna, detecting the electrical fields of prey hidden in the current.

The current at The Magnet can be powerful — strong enough to rip your mask off if you face into it, strong enough to push you away from the pinnacle into open blue water if you are not positioned correctly. The dive plan, explained in the briefing, involves using the pinnacle as shelter from the current, staying on the downstream side where an eddy creates relative calm, and ascending along the pinnacle structure rather than fighting the current to return to the entry point.

### Cathedral

A dramatic wall dive where the reef face is sculpted into overhangs, arches, and cavern-like formations that create the cathedral-like ambiance of the name. The wall drops from 10 meters to beyond 40 meters, with the best hammerhead viewing along the lower sections (25-35 meters) where the sharks cruise parallel to the wall face.

Cathedral is slightly less current-exposed than The Magnet, making it a common first-dive site for groups testing conditions. The wall structure provides natural current shelter — you can tuck behind overhangs and peer out to watch the sharks pass. The wall itself is encrusted with soft corals, sea fans, and sponges in colors that range from deep purple to vivid orange, creating a spectacular backdrop for the shark encounters.

### Belongas Reef

A shallower site (10-25 meters) used for second dives and conditions assessment. The reef is less dramatic than The Magnet or Cathedral but rich in macro life — nudibranchs, frogfish, octopus, and the small reef fish that make up the base of the bay's food chain. Manta rays and eagle rays are sometimes encountered here, cruising over the reef on feeding passes.

### Preparation

A Belongas dive trip begins the evening before with a briefing from the dive operator. This is not a perfunctory safety talk — it is a detailed explanation of the conditions you will face, the dive plan for each site, the emergency procedures for current separation, and the communication signals specific to Belongas diving.

Key briefing points include:

• How to recognize and respond to thermoclines (the sudden cold does not mean something is wrong — it means you are in the zone where the sharks are)
• Drift diving procedures: how to deploy an SMB at the end of the dive, how the pickup boat will find you, and what to do if you surface away from the boat
• Current management: how to read the current direction from the surface, how to use reef features for shelter, and when to abort a dive if current exceeds safe levels
• Shark behavior: hammerheads are not aggressive toward divers, but approaching too closely or ascending directly into a school can cause them to disperse — stay on the bottom, stay still, and let them come to you

### The Dive

Morning arrives early — most operators depart at 6 or 7 AM for the best hammerhead encounters. The boat ride from Kuta to the bay takes 30-45 minutes, during which you suit up, check equipment, and study the surface water for current indicators.

The entry is a negative entry: you jump from the boat with fully deflated BCD and descend immediately, equalizing quickly and efficiently as you drop past 5, 10, 15, 20 meters. The reason for the negative entry is current — if you surface-swim to the dive site, the current may push you past it before you can descend. By entering and descending immediately, you reach the protected zone of the dive site before the current can carry you away.

At depth, the water changes. The warm surface layer gives way to a thermocline — a shimmering, watery boundary where cold deep water meets warm surface water. You swim through it and the temperature drops 5-10 degrees in seconds. Your body registers the cold as a shock, then adjusts as your wetsuit insulates. You are now in hammerhead territory.

The sharks may appear immediately or may require patience. Often, they materialize from the blue — dark shapes that resolve into hammerheads as they approach, their wide, flat heads swinging rhythmically as they swim. They may pass at distance (10-15 meters) or come close enough to fill your field of vision. The experience of being at depth, in cold water, in current, watching 20 hammerhead sharks swim past you in formation, is one of the most intense and rewarding experiences in recreational diving.

### After the Dive

Surface intervals between dives are spent on the boat, warming up, hydrating, and debriefing the dive with your guide. The conversations among divers after a hammerhead encounter have a particular quality — a mix of adrenaline, disbelief, and the satisfaction of having worked hard for a reward that delivered beyond expectations.

A typical Belongas day involves two dives: the deep, challenging first dive at The Magnet or Cathedral for hammerheads, followed by a shallower, more relaxed second dive at Belongas Reef for reef life and warmth recovery. Some operators offer three-dive days for those with the stamina and air consumption to handle them.

Belongas Bay is for experienced divers who meet specific criteria:

Certification: Advanced Open Water minimum. Deep Diver specialty is strongly recommended. Nitrox certification is valuable for extending bottom time and reducing decompression risk.

Experience: Minimum 50 logged dives, ideally more. Experience with current diving, deep diving (30+ meters), and cold-water diving is important. If your dive log shows only warm, calm, shallow tropical dives, you will find Belongas conditions challenging.

Physical fitness: The diving is physically demanding — swimming against current, managing buoyancy in cold water, and executing controlled ascents all require fitness and endurance.

Equipment: Own mask, computer, and wetsuit (5mm minimum). Rental equipment is available but your own gear, properly fitted and familiar, adds a significant comfort and safety margin.

Mindset: Comfort with uncertainty. Belongas conditions are variable — current strength, visibility, temperature, and marine life encounters change from dive to dive. The willingness to accept that a dive might not deliver the shark encounter you hoped for, and to enjoy the diving experience regardless, is important.

Belongas Bay is not exclusively about hammerheads. The bay's marine ecosystem is rich and varied, and divers who focus only on shark encounters miss much of what makes the area special.

Manta rays — both reef mantas (Mobula alfredi) and occasionally the larger oceanic manta (Mobula birostris) — visit Belongas for cleaning and feeding. Their arrivals are less predictable than the hammerheads but equally spectacular. A manta encounter at Belongas typically involves the ray swimming directly overhead, its massive wingspan (3-5 meters for reef mantas, up to 7 meters for oceanics) blocking the sunlight momentarily as it passes.

Mobula rays — the smaller cousins of mantas — sometimes aggregate in Belongas in schools of dozens or hundreds, creating a visual spectacle of diamond-shaped bodies swooping and turning in synchronized formation.

The reef itself supports a healthy population of reef fish, including some species that are uncommon or absent at the Gili Islands' more frequently dived sites. Macro enthusiasts will find nudibranchs, pipefish, and various crustaceans in the crevices and overhangs of the wall faces.

Hammerhead sharks are classified as Critically Endangered by the IUCN, primarily due to overfishing for their fins (used in shark fin soup) and bycatch in commercial fishing operations. Their aggregation at sites like Belongas Bay — where they are predictable and concentrated — makes them vulnerable to targeted fishing.

Indonesia has enacted some shark protections in recent years, and Lombok's dive community is increasingly vocal about the value of live sharks for tourism versus dead sharks for fins. A single hammerhead encounter at Belongas generates dive-trip revenue that far exceeds the one-time value of the shark's fins. This economic argument — that live sharks are worth more than dead sharks — is the most practical tool for conservation in communities where fishing is the economic foundation.

Divers who visit Belongas contribute to this economic argument simply by paying for the experience. The money flows to dive operators, boat crews, and local communities, creating a financial incentive to protect the sharks rather than catch them. It is an imperfect conservation mechanism, but it is the one that works in the real world of Indonesian coastal economics.