A remotely-operated vehicle being used in the Cayman Trough, a deep trench formed at the boundary between two tectonic plates, found the 30-foot-tall vents belching superhot black water almost 16,500 feet below the ocean surface, the BBC reported Thursday.
The researchers on the expedition funded by Britain's Natural Environment Research Council said they measured the temperature of the inky water spewing from the jets at more than 750 degrees Fahrenheit, making the vents among the hottest on the planet.
Chief scientist Jon Copley of the National Oceanography Center called the discovery of the "astounding mineral spires" a "complete surprise."
"We initially thought it was a site we'd been to before but it looked so different we thought it had changed," he said. "But eventually we realized it looked different because it was different."
The researchers said they would be making further dives in the area, while Japanese and American researchers are planning investigations in the Cayman Trough later in the year.