On the last full day of the holiday, after the gf had injured her foot, I went on a guided walk out to the reef.
It was about a kilometer out, and I was shown various creatures by the beach boy (who was probably my age actually).
This is a male starfish (the females are 5 sided blobs), and I was told that there are also green and blue versions of this.
You can see some damage to the end of the lowest ‘arm’ – this is where it had been nibbled at by a __ (I forget), and it was unable to move away from it. (I have video of Spider Starfish moving – it’s quite bizarre that they can even choose a direction to move!)