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 know, but they don’t only occur in warm waters. In some of the oceans coldest, darkest depths they are thriving. The deep water reefs are formed by icebergs as they slide across the sea bed, leaving behind 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. Underwater cameramen have ventured down to the pitch blackness to find life thriving. In this one hour HD special, our team will enter this alien environment. And discover a strange, hidden world abundant with life, from the weird to the wonderful.