It was extraordinary for scientists to see underwater animals going about their business as usual amidst what were previously considered inhospitable temperatures and acidity levels.
Ocean engineer Brennan Phillips, who led a team of researchers to the Soloman Islands to investigate the hydrothermal activity said, reported io9: "The idea of there being large animals, like sharks, hanging out and living inside the caldera of this volcano conflicts with what we know about Kavachi, which is that it erupts.
"But when it erupts, there's no way anything could live in there. And so, to see large animals like this that are living, and potentially they could die at any moment, it brings up lots of questions: 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 team dropped a deep-sea camera into the crater, since the main peak of the volcano, Kavachi, was not erupting at the time.
When the camera arrived back on the surface, the footage showed hammerheads and silky sharks smoothly swimming away, despite the previously perceived hostile environment undersea.
"You never know what you're going to find. Especially when you are working deep underwater. The deeper you go, the stranger it gets," said Phillips.
"No one has ever looked in the deep sea there, period. No one's been out to anywhere in the Solomon Islands and gone deeper than a few hundred meters or deeper than a scuba diver has gone, really. So we were very excited. We thought there was a lot of potential.
"They're in there, in numbers, inside the volcano! Now I want to spend years trying to study that and why that is the case."