The planarian is a flatworm, a multi-celled animal with cilia on the bottom surface and around the tail that it uses for swimming.
Planaria are hermaphroditic, meaning they are both male and female. They meet to swap sperm, which fertilizes the eggs that develop in two rows along the side of the body, easily seen in the photo above and the videos below.
The planarian has two eyespots in the triangular head, and a mouth on the under surface. They have no internal body cavity to hold organs, no circulatory system, and their intestine has no opening at the rear end. They can reproduce asexually by splitting in two, with the head growing another tail, and the tail growing another head. You can cause this to happen by cutting one in half with a razor blade.
In the video below, you can see the debris in the water being moved around by the motion of the planarian's cilia.