Flatworms living on leather coral

Anyone know these very interesting looking worms. Photo from Great Barrier Reef, Australia

It belongs to the poorly known flatworm group known as Acoela. The genus most frequently cited is Waminoa, which is described as being pumpkin pr disk-shaped, and some species have a yellow spot near the posterior end. Maybe your critters belong to this genus?

Thanks Leslie, Waminoa does look like a good match.