Ask geophysicist Guust Nolet of the University of Nice in France if mermaids exist and he will tell you “Yes! And I love them!” He admits they are, of course, a rarity in the ocean. He’s currently tracking two in the Mediterranean and four in the Indian Ocean. And if you want to hear them sing, you’ll have to wait 10 days for them to come to the surface, unless there’s been an earthquake.

Wait what?

Yep, these mermaids are seismically sensitive and Nolet and his team of oceanographers from the United States and France have deployed everyone of them.

PHOTOS: Sea Monsters Real and Imagined

For the first time oceanographers have a fleet of floating seismic detectors cruising the seas. The Mermaids (Mobile Earthquake Recording in Marine Areas by Independent Divers), provide seismic coverage of a large swath of Earth that is mostly invisible to seismologists: the oceanic crust. Unlike ocean bottom seismometers that are stuck on the seafloor for sometimes a year or more at a time, and have to be retrieved using expensive ship time expeditions to learn what data they have recorded, Mermaids will pop to the surface and transmit their data whenever they receive a signal that has a 90 percent chance of being an earthquake.

Turns out most magnitude 6.5 earthquakes can trigger enough commotion, in the form of bubbles and seafloor rumbling, to rise above the din of the regular ocean noise. “We’ve seen magnitudes as low as 5.5 as far away as Mexico,” Nolet told reporters at the American Geophysical Union in San Francisco today.

Quakes Could Trigger Massive Supervolcano Eruptions

They track the earthquakes in a similar fashion to land seismometers, only their mobility also gives the Mermaids an advantage for recording additional details from any large aftershocks from an earthquake. For example, during a seismic swarm in the Indian Ocean on Nov. 25, 2013, seismic stations on land captured only two events, whereas one of the Mermaids recorded nearly 200 “triggers” in 13 seismograms.

Undersea Volcano Erupts A Mile Below The Surface

They can also speak whale. Of course you’d expect mermaids to do so. The noise signatures for whale songs are distinct for each species. Nolet and his team are recommending other scientists take advantage of their Mermaids by including biological and meteorological sensors onto their divers. Each Mermaid can dive down to as far as 2,000 meters.

Next year the team plans to deploy 10 Mermaids around the Galapagos Islands to monitor the seismic signatures from the volcanic magma plume that feeds the islands.