After nearly a year of exploration, Chinese researchers have discovered an underwater sinkhole that is likely the world’s deepest, reaching about 987 feet below the surface and surpassing the previous record holder, Dean’s Blue Hole near the Bahamas, by more than 300 feet.

According to the report, Blue holes are named as such for their rich, dark blue coloring, a stark contrast to the otherwise aqua waters that surround them. Researchers with the Sansha Ship Course Research Institute for Coral Protection began exploring Dragon Hole, known as Longdong, in August 2015 and completed the project last month, Xinhua reported. …