Senckenberg Naturmuseum, Frankfurt am Main, Germany.
Brain coral is a common name given to corals in the family Faviidae, so called due to their generally spheroid shape and grooved surface which resembles an animal brain. Each head of coral is formed by a colony of genetically identical polyps which secrete a hard skeleton of calcium carbonate; this makes them important coral reef builders like other stony corals.
That's a brain coral.
A very dead brain coral.
I was thinking the same thing, Katharine. Looks like it got bleached. Still a very beautiful pic though, I love seeing this stuff when I dive.