The overgrowth of outer ear canal bone is the body's way of protecting the ear drum from the frequent rush of cold water against it which commonly occurs with surfing. They develop over many years and result in infections, pain, plugging and hearing loss.
When used in the phrases "Cartilaginous exostosis" or "Osteocartilaginous exostosis", it is considered synonymous with Osteochondroma. Some sources consider the terms to mean the same thing even without qualifiers, but this interpretation is not universal." Source: Wikipedia