Tun Sakaran Marine Park
Most guests step onto a Semporna boat expecting a vertical limestone wall falling into the abyss. Sipadan trains you to look down. Tun Sakaran Marine Park trains you to look at the rubble and the sand. I have run this northern route a hundred times and it remains the best antidote to a week of heavy current. This is not a substitute for the big open-water encounters. It is a vast flooded volcano that offers the finest shallow reef flats in Sabah.
Table of Contents
- The geography of a flooded caldera
- Bohey Dulang: a hike with a view
- Mantabuan: the shallow mesh reef
- Sibuan: the battleship sand cay
- The patch reefs: Church and Kapikan
- How the day runs from Semporna
The geography of a flooded caldera
The park covers 350 square kilometres. It is an archipelago built from the remnants of an extinct volcano. Bodgaya and Bohey Dulang form the steep outer rim of this ancient crater. They encircle a lagoon that drops 25 metres deep. The dark grey volcanic rocks date back to the Pliocene and Quaternary periods. The southern islands like Sebangkat and Selakan sit on raised limestone platforms rather than volcanic rock.
This topography changes the water. The islands and their networks of reef break up the ocean swell. The water inside the lagoon sits still and lets fine sediments settle onto the seabed. That stillness creates a huge nursery for young fish and small creatures that are good at hiding.
The volume of life here competes with any wall in the Coral Triangle. I dive among 44 different species of mushroom coral. That is a global record held right here in these shallow basins. You do not come here for the sharks. You come here to find the oddest things on the reef.
Bohey Dulang: a hike with a view
Bohey Dulang is a hike with a panoramic view. You do not dive it. The boat ties up at the wooden jetty and you head up a steep track of exposed tree roots and loose volcanic dirt. The trail climbs between 600 and 700 metres to reach a rocky peak 353 metres above the sea. The ascent takes forty-five minutes if you have good lungs.
The view from the top gives you the entire flooded caldera. You see the deep sapphire blue of the inner lagoon sharply divided from the mint green of the shallow coral platforms.
Sabah Parks runs a tight operation here. You must wear closed-toe trainers or proper hiking boots. The rangers check your feet at the trailhead and they will deny you entry if you show up in sandals. The old shoe rental stand at the base is permanently closed. You must bring your own shoes. Children under six years old are banned from the trail for their own safety. They stay at the jetty with the boat crew. The trail shuts down immediately during rainfall to prevent accidents on the mud.
The trail passes through an odd patch of scrub forest. The volcanic soil supports an isolated pocket of flora. These plants share more botanical history with the Philippines than with the rest of Borneo. You walk past a plant called Dracaena multiflora that looks like a giant cycad. It grows ten metres tall out of the volcanic rock. The island canopy hides Pied Hornbills and Nicobar Pigeons. Watch the shallows around the jetty when you return. I often spot a banded sea krait as it hunts in the rocks.
Next to the jetty sits a wooden hatchery over the water. Researchers breed seven species of native giant clam here to reverse decades of poaching. The tanks hold Tridacna gigas specimens alongside the China clam. Breeding them is a delicate act. The clams get nutrients from algae that use sunlight to make food inside the clams' fleshy tissue. Less than three percent of the fertilised eggs survive to reach one inch in size.
Mantabuan: the shallow mesh reef
Mantabuan is the smallest island in the park. It covers a mere ten hectares. Do not let the size fool you. It sits surrounded by a complex network of mesh reefs that drop down to 35 metres facing the open bay.
Mantabuan suits a boat with both snorkellers and divers. Snorkellers can drop into four metres of water to float over a brightly lit coral garden. Divers can roll off the same boat and drop down the slope to hunt through the deep black coral trees. I have seen blue-spotted ribbontail rays spread across the seabed at Stingray Alley. Both groups have room to explore without the captain having to burn fuel to move the boat.
The reef here is a live laboratory. Sabah Parks maintains 95 hexagonal metal frames across the seabed. They coat the metal in sand and plant it with fragments of branching coral to rebuild sections of damaged reef. The fish treat it like a newly opened apartment building. Small-tooth whiptails and fusiliers swarm the structures. You swim past them and see the exact mechanics of how a reef recovers. Mantabuan also holds crucial habitats for rare coral species like Heliofungia actiniformis.
Sibuan: the battleship sand cay
Sibuan is a teardrop of bright white sand. A tight cluster of tall coconut palms sits in the middle. The long sand spits taper off into the water to give it the local nickname of the Battleship.
This is the muck diving capital of the park. The island acts as a natural shelter. The gentle coral drop-offs protect fine sediments and create a sanctuary for tiny marine life. The sandy slopes drop away gently between five and 25 metres. I take you to sites like Left Shoulder and Mandarin Point to hunt. Frogfish wait in the rubble to perform their patient ambush act. Ornate ghost pipefish hover head-down next to the coral blocks. Ribbon eels stretch out of their holes to snatch passing food. You need flawless buoyancy to dive here. One lazy fin kick will stir up the silt and ruin the visibility for everyone behind you.
The island itself has zero tourist facilities. There are no toilets and no restaurants. You pack your rubbish out when you leave. You can use a drone at some locations across the park but Sibuan island is a complete no-fly zone. Keep the camera in your bag until you are underwater.
The patch reefs: Church and Kapikan
Some of the best sites in the park have no dry land attached to them at all. Church Reef and Kapikan Reef are huge coral patch reefs. They rise from the depths to form sprawling platforms just below the surface.
Church Reef runs for 7.5 kilometres around its rim. The reef flat sits in a single metre of water. Snorkellers can glide over broad stretches of healthy hard coral. The northwestern edge drops into a vertical forty-metre wall. I send divers down the wall to look for pygmy seahorses in the deep sea fans.
Kapikan Reef sits further east and takes the full force of the open ocean. The eastern flank plummets 130 metres down. That deep oceanic exposure brings the clearest water in the entire park. You fight stronger currents here. The reward is broad fields of hard coral and regular sea turtle sightings.
How the day runs from Semporna
Tun Sakaran is exclusively a day trip. The law prevents any public accommodation inside the park boundaries. You sleep elsewhere and commute in.
Most boats leave the mainland Semporna jetty at eight in the morning to beat the equatorial heat. The speedboat ride takes forty-five minutes. If you stay on Mabul the transit takes an hour and a half across the bay. I always head for the Bohey Dulang hike first. You want to finish the climb before the sun bakes the volcanic rock.
The boat then moves to Mantabuan for a mid-morning session in the water. Lunch happens on the deck or on a beach before you finish the day hunting for frogfish at Sibuan. The boats run back to town by four in the afternoon. The boat passes the shallow flats of Sebangkat and Selakan where local Bajau Laut communities farm seaweed. They live in wooden houseboats or in stilt houses suspended directly over the reefs. You must always ask for explicit permission before you photograph individuals or their homes.
You need to pack smart. Sabah Parks enacted a total ban on single-use plastic bags in January 2026. The rangers enforce it. Bring your gear in a proper dry bag and pack a reusable water bottle.
Keep this itinerary in your back pocket for November. Sipadan shuts down completely for a month of marine rehabilitation every November. Tun Sakaran Marine Park stays fully open. It acts as the premium alternative when the big wall is closed.
A rest day from the deep open-water sites gives you time to appreciate the small things. See Semporna mainland resorts or Mabul dive packages to find a base camp. Tell us your dates and we will match the boat to your group.