Scientists studying sharks’ mating patterns can finally understand what they see in each other.

By augmenting a camera to see colors the way two species of catsharks do, researchers with the Museum of Natural History were able to gain “shark vision” deep under the waters of Scripps Canyon, San Diego.

While human eyes would barely register anything in the murky depths, the camera showed the catsharks clearly—in bright green.

The researchers say this was caused by biofluorescence, a phenomenon by which some sea creatures give off a subtle green glow—subtle to our eyes, but not to the sharks’.

Scientists believe this glow is used to help the sharks find a mate. And one can see why—while to people most sharks are harsh, gray creatures, to each other they’re magnificent visions in green.