Many sounds are almost unnoticeable, but several marine species produce sounds that can dominate a soundscape. Marine animals, including fish and invertebrates, produce sounds to communicate but also use sound to interpret their surroundings, for example to detect prey or predators or to find a proper habitat. However nowadays, anthropogenic noise dominates most of the marine environments. In this activity we will learn about sounds that can be detected underwater and use a hydrophone to "hear like the fish" in Porto da Baleeira.