These pictures were taken in places where it inhabits. In a coastal pool of sand and shell fragments. In the littoral zone of the Indian Ocean, in Sumatra. The scientific name of this algae species is Padina pavonica. It appeared to be shaped like a fan or funnel. I took pictures of the algae when the tide was very low, and the pool was very shallow. Sunlight falling on the surface of the water looks like it is being edited by ripples to form lines of light that are very characteristic of liquid at the bottom of a pool.
Turns out, this one was there too. It camouflages and hides in the surrounding environment. It was very quiet, and seemed unwilling to stand out. I think it also chews Padina pavonica.