Belongas Bay Diving: Hammerheads, Mantas, and Deep Walls

While the Gili Islands provide Lombok's bread-and-butter diving with gentle reefs and abundant turtles, Belongas Bay is where the serious stuff happens. This remote bay on Lombok's far south coast sits at a geographic crossroads where deep oceanic currents sweep past the coastline, creating conditions that attract the kind of marine life that makes experienced divers tremble with anticipation.

The bay's underwater topography is dramatic — seamounts rise from depths exceeding 40 meters, walls drop vertically into the abyss, and channels funnel current-driven water through narrow passages. This combination of deep water, current, and underwater structure creates a feeding station that draws in pelagic predators from the open ocean. Hammerhead sharks, manta rays, mobula rays, thresher sharks, and schools of tuna and trevally all patrol these waters at different times of year.

Belongas is not for everyone. The currents can be strong and unpredictable. The depths are significant. The water temperature drops sharply below thermoclines. And the remoteness means that evacuation in case of emergency takes considerably longer than from the Gili Islands. But for qualified divers who accept these challenges, Belongas offers encounters that rank among the best diving experiences in Indonesia — a country that is itself one of the world's great diving destinations.

The bay has been gaining recognition in the international diving community over the past decade, with underwater photographers and videographers producing stunning footage of hammerhead schools and manta encounters. Despite this growing reputation, Belongas remains relatively uncrowded compared to similar big-animal dive sites in places like the Galapagos, Maldives, or Komodo. On any given day, you might share the Magnet with just one or two other dive boats — a luxury at a world-class site.

The Magnet, also known as The Cathedral, is the dive site that put Belongas Bay on the global diving map. A massive underwater seamount rises from the deep ocean floor to about 12 meters below the surface, creating a geological feature that acts as a magnet for marine life — particularly schooling scalloped hammerhead sharks.

The dive typically begins with a descent from the boat down to the top of the seamount at 12-15 meters, where you orient yourself and check conditions. From here, you descend along the seamount's wall to 25-30 meters, where the hammerheads most commonly school. The sharks circle the mount in loose formations, sometimes in groups of 5-10, occasionally in schools of 30-50 or more. They emerge from the blue water like ghosts — their distinctive silhouettes unmistakable even at distance.

The experience of watching hammerhead sharks is profoundly different from seeing reef sharks. Hammerheads are open-ocean predators with an alien appearance — the wide, flattened head with eyes at each end gives them an otherworldly quality. They move with a slow, deliberate grace that belies their power. When a school passes overhead, blocking out the light from above, the scale of the encounter becomes overwhelming. This is one of diving's peak experiences.

However, hammerhead encounters are not guaranteed. The sharks are wild animals responding to water temperature, current, season, and factors we do not fully understand. On some dives, you will see dozens. On others, the blue water remains empty. This unpredictability is part of the Magnet's character — every descent carries the thrill of possibility.

Dive profile: Surface to 12 meters (seamount top), descend to 25-30 meters along the wall, maintain depth while scanning the blue water for sharks, ascend gradually, safety stop at 5 meters. Total bottom time: 35-45 minutes depending on air consumption and depth. Nitrox (enriched air) is recommended to extend bottom time at depth.

Conditions: Current at the Magnet ranges from moderate to very strong. On strong current days, the dive becomes a reef hook dive — you hook onto a rock or dead coral to hold position while the current flows past you and the sharks swim by. Your guide will carry reef hooks and demonstrate their use in the pre-dive briefing. Downcurrents are the primary hazard — if you feel yourself being pulled deeper, inflate your BCD and swim laterally away from the mount.

Belongas Wall: A vertical wall dropping from 5 meters to well beyond recreational limits along the outer edge of the bay. The wall is covered in healthy soft corals — sea fans, whip corals, and branching soft corals in pink, purple, orange, and yellow create a kaleidoscope of color. White-tip reef sharks rest on ledges at 15-20 meters. Turtles glide along the wall face. Schools of anthias swarm the upper sections.

The wall dive is less extreme than the Magnet and is suitable for Advanced Open Water divers. Current varies — on calm days it is a gentle drift, on strong days you need to fin against the flow or use reef features for shelter. The wall's beauty makes it an excellent second dive after a Magnet session.

The Playground: A relatively sheltered site inside the bay with a mix of coral garden, sandy slopes, and scattered bommies at 10-22 meters. This is the most accessible dive in Belongas, sometimes suitable for confident Open Water certified divers when conditions are calm. The marine life is diverse — blue-spotted stingrays on the sand, cuttlefish hunting among the coral, nudibranchs on dead coral rubble, and occasional reef sharks passing through.

The Playground lacks the dramatic big-animal encounters of the Magnet but offers a more relaxed dive experience that lets you focus on the smaller things. Many divers find it a welcome contrast to the intensity of the deep sites.

Gili Sarang: A small island east of the main bay with excellent wall diving and healthy reef systems. Less frequently dived than the Magnet and Belongas Wall, making it feel genuinely exploratory. Trevally and barracuda school in the currents, and the coral coverage is among the best in the area.

Different species appear at Belongas Bay at different times of year, influenced by water temperature, currents, and plankton cycles:

September-December (peak season): The highest probability of hammerhead shark encounters. Cold upwellings bring nutrient-rich water that attracts pelagic species. Manta rays arrive to feed on plankton. Mobula rays form schools in the hundreds. Thresher sharks are occasionally spotted. Water temperature at depth can drop to 18-22°C due to thermoclines.

January-April: Hammerheads remain present but in smaller numbers. Whale sharks make occasional appearances, attracted by plankton concentrations. Warm surface water makes boat transit comfortable. Good period for combining Belongas dives with Gili Islands diving.

May-August: The dry season brings excellent visibility (25-30+ meters) but fewer pelagic encounters. Reef life is vibrant and the walls are spectacular for photography. Currents tend to be more moderate. This is a good period for less experienced divers to try Belongas's shallower sites.

Current: The defining characteristic of Belongas diving. The bay sits where oceanic currents meet the coastline, creating flow patterns that can range from gentle drift to powerful surge. At the Magnet, current is almost always present and can change direction and intensity during a dive. Downcurrents — vertical flows pushing divers deeper — are the primary hazard and require immediate response (inflate BCD, swim laterally).

Temperature: Surface water stays at 27-29°C year-round. Below the thermocline (typically at 15-25 meters), temperature can drop dramatically to 18-22°C. This cold water is uncomfortable and can cause shock if unexpected. A 5mm full wetsuit or 3mm wetsuit with hooded vest is recommended for Belongas diving. You will be cold after a deep dive — bring warm clothes for the boat.

Visibility: Highly variable. Surface visibility is often excellent (20-30 meters) but can drop below the thermocline to 10-15 meters. The reduced visibility below the thermocline, combined with the dark color of the deep water, creates an eerie atmosphere that enhances the impact of shark encounters — they appear and disappear like apparitions.

Minimum requirements: Advanced Open Water certification. Comfortable with depths of 25-30 meters. Experience with currents. Minimum 30-50 logged dives (varies by operator). Good buoyancy control. Physical fitness — Belongas dives can be physically demanding. Honest self-assessment of your skills and comfort level.

Equipment recommendations: Personal dive computer (do not rely on the guide's). Surface marker buoy (SMB) — essential if you surface away from the boat in current. Dive torch for looking into crevices on the wall. Reef hook for the Magnet. 5mm wetsuit. Nitrox certification allows safer extended bottom times at depth.

From Kuta Lombok: The standard route. Drive east along the south coast road through Awang and on to Belongas. The road is paved and scenic, winding through traditional Sasak villages with views of terraced hillsides and distant ocean. Total driving time: approximately 2 hours. Most dive operators include transport in their package.

Typical day trip schedule:

• 5:30-6:00 AM: Hotel pickup in Kuta Lombok
• 7:30-8:00 AM: Arrive at Belongas, boat preparation
• 8:30 AM: First dive (usually the Magnet)
• 10:00 AM: Surface interval, snacks, tea
• 11:00 AM: Second dive (wall or Playground)
• 12:30 PM: Lunch at the beach
• 1:30 PM: Drive back to Kuta
• 3:30-4:00 PM: Return to hotel

Multi-day trips: A few operators offer 2-3 day packages with accommodation near Belongas, allowing for early morning dives (best for hammerheads) and multiple dives per day. These packages cost 2,500,000-5,000,000 IDR per person including accommodation, meals, and 4-6 dives. Recommended for serious divers who want to maximize their chances of big animal encounters.

What to bring: Warm clothes for after diving, motion sickness tablets for the boat ride, plenty of water, sunscreen, camera (if you have an underwater housing), and cash for any additional charges.

Several operators run trips to Belongas Bay from different bases around Lombok. Key factors for choosing an operator:

Local knowledge: Belongas is a site where guide experience matters enormously. Operators who dive the bay regularly know the current patterns, the best entry points for different conditions, and where to position divers for the highest probability of shark encounters. Ask how frequently they run Belongas trips and how long they have been diving the bay.

Safety equipment: Every dive boat to Belongas should carry oxygen, a first aid kit, emergency communication, and enough surface marker buoys for all divers. Ask about these before booking.

Group size: Smaller groups (maximum 4-6 divers) allow better management in currents and more personalized attention. Some operators pack 8-10 divers per guide at Belongas, which is too many for the conditions.

Flexibility: Good operators will adjust the dive plan based on conditions. If the current at the Magnet is too strong for the group's experience level, they should redirect to a safer site without complaint. An operator who insists on diving the Magnet in dangerous conditions is prioritizing reputation over safety.

Prepare physically and mentally. Belongas demands more from your body and mind than gentle Gili reef dives. Get a good night's sleep, hydrate thoroughly, eat a light breakfast, and avoid alcohol the night before. Mental preparation is equally important — review your deep diving skills, refresh your current management techniques, and visualize the dive profile.

Arrive with adequate experience. If your Advanced Open Water certification is fresh and you have only logged a handful of dives since, consider getting more experience at the Gili Islands before tackling Belongas. The currents and depths here are not appropriate for building basic skills.

Listen to the briefing. The pre-dive briefing at Belongas is not a formality — it covers specific current conditions, entry and exit procedures, emergency protocols, and what to do if separated from the group. Pay close attention and ask questions if anything is unclear.

Stay close to your guide. In strong currents with limited visibility, losing visual contact with your guide is dangerous. Maintain a distance of no more than 3-5 meters. If you lose the group, deploy your SMB, ascend slowly, and wait at the surface for the boat.

Manage your air. Deep diving and current swimming consume air faster than shallow reef dives. Monitor your gauge frequently and signal your guide when you reach 100 bar and again at 70 bar. Plan your ascent with enough air for a comfortable safety stop.

Stay warm. Cold water at depth saps energy, impairs judgment, and increases air consumption. Wear adequate thermal protection. If you start shivering during the dive, signal your guide and begin your ascent — hypothermia is a serious risk at depth.

Keep expectations realistic. Even during peak season, hammerhead encounters at the Magnet are not guaranteed. Some days you will see spectacular schools of sharks. Other days, the blue water will be empty and you will spend the dive admiring the seamount's coral and reef life. Both experiences have value, and approaching the dive without rigid expectations makes it more enjoyable regardless of what appears.