Just as a cat will follow a bright spot along the wall or floor, so will an otter or seal or many other kinds of mammals or fish follow this bright green spot. The bright green spot moving along the surface of a rock, a hard coral face or along the bottom attracts their attention the same as the light reflecting from the side of a delicious little fish with shiny scales. It's not even necessary to be interested in taking a picture to enjoy this feature of the green laser. It's great fun to watch a sea otter or seal chasing the green spot as you move the beam back and forth.
Simulated image of laser.