Mysterious Starfish is the forth coral on the coral list, appearing to be some form of large starfish with a yellowish-orange body and bluegreen stripes pointing to the middle. It is required to unlock the first two Tang, Blue Tang and Achilles Tang.
No coral is known to exist that looks like the Mysterious Starfish, however, there are two starfish that it could be based off of. Looking up "mysterious starfish" lead to an article talking about a mysterious disease that currently plagues starfish populations, with a picture of a "Solaster stimpsoni" or "Striped Sunstar." In terms of colour and "large size," the starfish matches the Mysterious Starfish surprisingly well, besides the exaggerated size and lack of legs that the real-life Striped Sunstar has. Another possibility is that it's based on a "Royal Starfish," which matches the number of legs and colour pattern, albeit heavily saturated.
- The icon for the Mysterious Starfish coral has inverted colours and a different pattern than its 3D model in the game
 Mysterious disease article (TW: Dying Starfish)
 Wikipedia: Striped Sunstar
 Wikipedia: Royal Starfish