All flatworms have a soft body and a triangle-shaped head. They also have eye-spots on top of their heads which can see light. Flatworms are not closely related to most other worms, such as earthworms. Bodies are flat instead of round, and they do not have segments.Flatworms spend most of their time on the bottom, especially since they can't swim.They release sticky mucus (a lot like slugs and snails) which they glide on top of.hey also have eye-spots on top of their heads which can see light. Flatworms are not closely related to most other worms, such as earthworms. Bodies are flat instead of round, and they do not have segments. Flatworms spend most of their time on the bottom, especially since they can't swim.