Coral reefs are some of the richest hotspots of biodiversity on the planet. The warm water reefs of the Pacific Ocean and Caribbean Sea are well known, but reefs don’t only occur in warm waters. In some of the ocean’s coldest, darkest depths they are thriving. Formed by icebergs as they slide across the sea bed, these deep water reefs leave behind the perfect foundations for coral to build upon. Hidden from view, they criss-cross the planet from the deep water tropics to the freezing Arctic. Some have never been explored by humans, but now underwater cameramen have ventured down to the pitch blackness to find life thriving. Who would have thought that such brilliant colours and creatures could thrive in such dark, cold waters?