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

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
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.
Bonto
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
Tikno
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.