FLATWORMS - POLYCLADIDA Flatworms can be found in all seas from tidal waters, down to depths of more than one hundred meters. The most varied are found in the Indo-Pacific region. Flatworms can be seen swimming free or crawling over the substrate, corals or rocks. They all have a flat oval-shaped body and whilst some are smooth, others can be warty. Most of the tropical flatworms are brightly colored and some are even known to imitate a nudibranch. There are species that are only a few millimeters in length, while the biggest grow up 15 centimeters long. All flatworms are hermaphrodite in that they have both male and female sexual organs. After copulation, a spiral-shaped egg-mass will be attached to the substrate. Flatworms are carnivores and they feed on small invertebrates, sponges, worms and tunicates. They heal very quickly if damaged and separated parts can develop into a new organism.