Now playing in the southwestern Pacific Ocean: Sharkcano—an underwater volcano filled with sharks.

Officially, the volcano is Kavachi. It’s named for a fire god of a nearby culture. Its base is about three-quarters of a mile deep.

Kavachi is one of the most active volcanoes on the planet—there’s almost always a little something going on. Its first recorded eruption came in 1939. Since then, it’s erupted at least eight more times, including a long-lasting one from late 2022 into ’23.

The eruptions produce big underwater plumes of gas, rock, and ash. Currents carry the plumes miles away, staining the ocean surface. Some eruptions send debris into the sky. They can even build islands up to about half a mile long. The islands don’t last long, though—wind and waves quickly wear them down.

An expedition in 2015 arrived during one of Kavachi’s rare quiet times. That allowed scientists to float above the volcano’s summit, where they could sample the water and rocks, map the crater’s contours, and look for life. And they found a lot of it. Big patches of microscopic organisms that feed on sulfur and carbon dioxide coated the volcano’s flanks. And snapper and other fish swam through the crater.

That included silky sharks and scalloped hammerhead sharks—inspiring Kavachi’s nickname. The sharks probably swim in and out over the crater’s rim. But they seemed to be doing well in the Kavachi’s hot, murky, acidic waters—living inside the Sharkcano.