Colpophyllia natans is a dominant reef-building coral with wide meandering valleys stretching across the entire surface of the coral colony. This coral forms impressive domed boulders and is one of the most common corals in the Caribbean.

The boulder brain coral is a familiar species on shallow reef ledges and slopes. It can be found down to a depth of 165 feet but is often established much closer to the surface.

Colpophyllia natans falls into the brain-coral category, and there are a few tricks to tell it apart from other species. First, Colpophyllia natans can grow into very large boulders — hence its common name — but if you’re met with a smaller colony, look closely at the small lines running from the top of the ridges to the center of the valleys.

The ridges of Colpophyllia natans remind me of a millipede, and that’s how I remember this species. The meandering ridges resemble the back of the millipede with the legs trailing into the valleys. In the center of the valley you will see that all the lines lead to a small circular mouth — this is the coral polyp.

During the day, the polyps are retracted inside the valleys. But at night, polyps will emerge and sticky tentacles will inflate to catch plankton in the current. Colpophyllia natans can be brown, tan, gray or white, while some colonies have dark ridges with vibrant green valleys. Most often its ridges and valleys will be of contrasting color.