Crown of thorns starfish are one of the sea creatures that caused damage to coral reefs. They fed on stony corals (Scleractinia). My friend Leo once joined a movement to collect this sea star somewhere in Samal Island because there was a population increase of this species in that area. Their consuming the reefs faster than it can regenerate itself.
Protoreaster nodosus covers a wide area of the shallow seawater. Also known as Horned starfish. You don’t want to step on it. Underwater, their spines really looked frightening to me, especially the large ones.