A healthy coral reef sounds like popcorn. Seriously: the hordes of snapping shrimp that fill their waters make create a constant crackling noise, something akin to crunching Pop Rocks or frying bacon. We humans can generally only hear this pop music by using hydrophones (underwater microphones), but fish and crustaceans use it to find their way back to their homes. Those fish aren’t silent, either; some belt out bubbling, frothing mating choruses, while others use sound to hunt prey. Taken together, these layers of sound help scientists create estimates of aquatic species diversity, and figure out how healthy a given reef is.

See, it isn’t just humpbacks that serenade the seas. In fact, the entire ocean is a more vibrant, dynamic soundscape than most people realize. After all, we tend not to pay attention to what's around us until it becomes a crisis (you don’t think about breathing until there's no air in your lungs; you don’t appreciate sleep until you haven’t gotten shut-eye for days). Now, as humans find ourselves interrupting the marine melodies that sustain our oceans, we’re realizing the many ways in which we've altered this soundscape before we’ve even gotten a chance to describe it.

Not all ocean sounds are made by nature. Humans make some of the newest—and loudest—addition to these soundscapes. Think about the impact on your life if you lived directly next to a highway. That’s what life is like for millions of fish and other sea creatures whose paths fall along shipping routes, or near construction sites, or in regions where underwater drilling is taking place. We still don’t know what 90 percent of fish sounds are, says scientist Julius Piercy, a UK government scientist who studies oceans and their sounds. And because we don’t have the data to know what these ecosystems should sound like, we have no idea of how our sound pollution is reshaping our underwater world.

So what can we do? Listen, appreciate, take notes—and try our best to preserve the marine symphonies happening right under our noses.