In 2015, scientists discovered sharks swimming calmly inside Kavachi, one of the world's most dangerous underwater volcanoes near the Solomon Islands. Kavachi often erupts lava, ash, and acidic water, making it a harsh place for fish. However, footage showed hammerhead sharks, silky sharks, and a stingray moving inside the volcano's crater unharmed. The expedition was led by ocean engineer Brennan Phillips, who used a deep-sea camera during a calm period when the volcano was not erupting. "Not only were silky sharks spotted in the area, but hammerheads too," Phillips said. "They appeared completely unfazed by the hot, acidic waters inside the volcano." The stingray seemed to shelter inside a small cave in the volcanic crater. Kavachi's crater is a caldera releasing superheated water, gases, and rocks during eruptions. Phillips said, "The idea of there being large animals like sharks hanging out and living inside the caldera... conflicts with what we know about Kavachi." He added, "Do they leave? Do they have some sort of sign that it’s about to erupt? Do they blow up sky high in little bits?" The discovery led to Kavachi being nicknamed "Sharkcano." Since then, NASA captured Kavachi erupting again in 2022, but it is unknown if the sharks survived. Due to eruption dangers, further studies used small, expendable robots to explore the volcano. These robots recorded hot water temperatures and acidity changes. Matthew Dunbabin explained, "No matter how well-built your systems are or how much they cost, it is very unlikely they will survive an explosion." Surprisingly, some volcanic rock stuck to the robots, giving scientists new samples. Phillips said sharks should not survive in Kavachi because it is "very hot and acidic," conditions hostile to most fish. Yet, sharks darted through volcanic plumes between eruptions. Scientists still do not understand if the sharks have unique behaviors or physical traits helping them survive. This rare find could teach us how marine life might handle extreme stresses, such as rising ocean temperatures. "That’s a lingering question mark," said Phillips.