In the terrestrial world, we rely heavily on optics and our vision, and less so on acoustics and hearing. In the ocean, the opposite is true. In coastal waters, light only travels relatively short distances (5-20m), so marine animals use light for sensing only the very near-field environment, while sound can travel huge distances (1-1000km), and informs marine animals of distant features and events. Marine scientists also take advantage of the efficiency with which sound travels in the ocean, and use it to both investigate and...