New research led by the National Oceanography Centre (NOC) has discovered how fast-moving waterfalls under the sea control the shape and behaviour of submarine channels. These underwater channels are the offshore equivalents of rivers, but can be much larger. Submarine channels can extend for tens to thousands of kilometres offshore, providing an important conduit for the transfer of sediment, nutrients and pollutants, such as microplastics, to the deep-sea. Avalanches of sediment that flow down these channels also pose a hazard to networks of seafloor cables that underpin global communications, including the internet.