https://www.vice.com/en_us/article/wxjdqb/mysterious-ocean-buzz-soud

Scientists have recorded the bustling sounds of underwater life in coral reefs off the coast of Goa, India, as part of a new study that revealed insights into marine biodiversity and detected a strange “buzz” call from a mysterious unidentified animal.

The research is part of a broader effort among marine biologists to use underwater sound recorders, known as hydrophones, to capture the soundscapes of aquatic wildlife around the world. Hydrophones can passively record underwater acoustics for days at a time, enabling scientists to eavesdrop on marine life to learn about their behavior, movements, and their response to environmental changes.