Silent marine robots that record sounds underwater are allowing researchers to listen to the oceans as never before. While pilot whales make whistles, buzzes and clicks, pods of hunting dolphins create high-pitched echolocation clicks and larger species such as sperm whales make louder, slower clicks. As well as eavesdropping on marine life, the recordings can be used to measure sea-surface wind speed and monitor storms. The research will be presented at the General Assembly of the European Geosciences Union, Vienna.