These high-temperature underwater vents are known as ‘black smokers’ because of the dense, black clouds they produce. They almost always occur at or near the summits of submarine volcanoes along the Kermadec Ridge. These underwater hot springs are rich in metal-bearing minerals. When the hot water discharging from the chimneys mixes with the surrounding colder sea water it cools rapidly, causing the metals to precipitate as particles. This video was taken during a combined expedition organised by GNS Science and JAMSTEC (Japan Agency for Marine – Earth Science and Technology).