Sangeang Volcano: Indonesia’s Best-Kept Diving Secret

It’s a shame that volcanoes have a bad reputation. Not that it’s their fault. There’s no denying that molten lava and impenetrable ash clouds sound intimidating. What you may not know is that volcanic debris is quite fertile. Underwater it transforms into a magical substance that hosts countless marine life. Some of the best macro diving in the world is often found around volcanic reefs – such as Sangeang Vulcano just of the coast of Sumbawa.

Sangeang volcano: Smaller eruptions occur on a regular basis

Nowhere is this coincidence better illustrated than in Indonesia, where biodiversity and volcanic activity combine to produce macro heaven! Due to the mineral-rich content, many rare and unique critters make their home in volcanic ash. If you like frogfish, pygmy seahorses, or mimic octopus, diving volcanic reefs is a must.

There are more than 125 volcanoes in Indonesia, but not everyone is lucky enough to host a reef nearby. Sumbawa, in the West Nusa Tenggara region, is home to one of the hidden gems of Indonesian diving: Gunung Api Sangeang.

Frog Fishes in various colors are are common sight around Sangeang volcano

Land sights on Sangeang Island

In addition to great diving and snoreklling sites, the fishing settlement by Bonto is a great cultural excursion. The villagers are descendants of the seafaring Bugis people from the Sulawesi. The Bugis are famed for their boat-building abilities and there is a traditional phinisi being assembled at Bonto. For a minimal charge, the villagers are happy to show you around the phinisi. Marvel at the ingenuity behind how a 30+ meter boat is built without a single nail or metal screw! The village also features traditional weaving and there is a hidden freshwater river.

Fabric making in a local village

Traditional Phinisi Yachts are built directly on the beach of Sangeang

Black Sands and Macro Diving Delights Around Sangeang

Situated about 10 kilometers offshore from Bima airport, Api Sangeang is an imposing, but scenic, volcano complex. There has not been an eruption since 2014, but its twin cones regularly send plumes of ash and smoke into the sky. Keep an eye out for wild horses, deer, mini buffalo, and goats that traverse the black sand beaches.

The underwater topography around Sangeang varies: sandy slopes tend to dominate most dive sites. Other sites feature coral outcroppings and a few walls. Nitrox is recommended if available. You’ll appreciate the extra bottom time when you lose yourself in the thrill of macro spotting.

Select liveaboards are the only ones that dive the area the rest of the year, so it never feels too crowded.

Best Dive Sites Around Sangeang

Hot Rocks

A site that appeals to macro and wide-angle enthusiasts alike. Underwater photographers will delight in the colorful coral ledges and the challenge of capturing nudibranchs only millimeters in length! The site’s most distinguished feature also happens to be the most accessible. At 3 meters you’ll find a sandy patch where hydrothermal vents release a constant stream of bubbles. The surreal experience feels like you’re diving in champagne. From 18 meters on, there are gorgonian fans where pygmy seahorses have been spotted. This site also features abundant black coral that are generally not found above 40 meters, elsewhere in the world.

Black Magic

Another black sand slope that is bookended by coral growth down to 30 meters. The bay is generally calm and serves as an ideal surface interval stop. Snorkelers can share in the same wonders as their diving counterparts due to the impressive visibility. Common sights include estuary seahorses, leaf scorpionfish, and demon stingers. Of note are the squarespot anthias found at depth and the saw blade shrimps in the black coral.


The island is uninhabited except for a small fishing settlement next to Bonto. If you’re in search of nudibranchs, this should be your first stop. Shaun the Sheep sea slugs (Costasiella sp.) are often spotted on green algae of the Avrainvillea species. Consisting of a gentle slope punctuated by coral outcroppings, you’ll find that sharp eyes and a slow pace are the key to uncovering Bonto’s treasures. The site is a favorite of mimic and long-arm octopus. frogfish, mantis shrimp and ghost pipefish.

A Mimic Octopus over volcanic sand


A deeper site, the sandy slope reaches down to 31 meters, below which is a drop-off. Black coral is abundant here, clustered on the sand off the wall. Another prominent feature is the sea whips, most of which have gobies living on them. Keep an eye out for orangutan crabs hiding in bubble coral, hawkfish amongst gorgonian, and ornate ghost pipefish. Be sure to check the large barrel sponges for hairy squat lobsters.

General Tips for Diving Sangeang

As with most muck sites, good buoyancy is critical. It’s easy to inadvertently silt out an area if you don’t practice situational awareness. Practice your frog kicks and work on perfecting your trim. Pointer sticks are a great tool for photographers to steady themselves in mild current.

The temperature of the water tends to be warmer than other sites around Komodo. Ranging between 25-28 degrees, a 3mm full wetsuit is usually enough exposure protection. Add a hooded vest or neutrally buoyant Sharkskin rashguard if you chill easily.

What About Safety?

While volcanic activity occurs with greater frequency in Indonesia, conditions around Sangeang have held steady since its last eruption. Indonesian authorities are vigilant in their monitoring of volcanic activities. Through apps, advance warning systems, and multi-agency oversight, risks are managed. Of course, travel insurance is always recommended, regardless of your destination. Barefoot Yacht can advise you of considerations for selecting the right policy.

Why Choose Barefoot

Api Sangeang still flies under most diving radars because only select operators know of its existence. Fewer still know are familiar with the location of dive sites. We provide our guests with honest and tailored recommendations for a Komodo liveaboard itinerary that includes unforgettable experiences like Sangeang.

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