Orange sun coral - Tubastrea sp. ?

Description:

Thisi is a large polyp stony coral found in Australian waters. Even though it is a stony coral, it is solitary so it's skeletons do not form reefs. It differs from many other stony corals in that it does not contain symbiotic algae - zooxanthellae - so does not derive food from sunlight. This means it can live in deeper waters. You can see in this photo that the polyp tentacles are clear - that is due to the absence of algae cells.