The brain or burned cabbage ascidian Trididemnum cerebriforme at Riy Banks, Algoa Bay , South Africa
Common fouling organism from Europe. Compare with Botrylloides, which can also be golden orange, but generally doesn't form radial, star-shaped colonies. Excellent description and record of introductions at http://www.exoticsguide.org/botryllus_schlosseri
Left hand side of the photo.
The brain or burned cabbage ascidian Trididemnum cerebriforme at Harlem Wreck, Algoa Bay, South Africa
Dive site Eidsvold, max depth 67 ft / 20.4m. Wreck of the Norwegian ship Eidsvold. Sunk in 1942 by a Japanese submarine; no casualties.
Ascidiacea (commonly known as the ascidians or sea squirts) is a class in the Tunicata subphylum of sac-like marine invertebrate filter feeders. Ascidians are characterized by a tough outer "tunic" made of the polysaccharide tunicin, as compared to other tunicates which are less rigid.