How do marine animals hear, see, touch, and smell the world around them? Life underwater is obviously very different to life on land and it can be difficult for us air-breathing humans to imagine what goes on down there beneath the waves. But understanding how animals find their way around the ocean plays a vital role in our efforts to conserve marine life. In this special edition of the Naked scientists, Helen Scales meets sensory biologist Jelle Atema from Boston University to find out what we know about the ways marine animals build a picture of the world around them.