For the time in which it lived, "Anomalocaris" was gigantic, up to long. It propelled itself through the water by undulating the flexible flaps on the sides of its body. Each flap sloped below the one more posterior to it, and this overlapping allowed the lobes on each side of the body to act as a single "fin", maximizing the swimming efficiency. The construction of a remote-controlled model showed this mode of swimming to be intrinsically stable, implying that "Anomalocaris" would not have needed a complex brain to manage balance while swimming. The body was widest between the third and fifth lobe and narrowed towards the tail; it was thought to have at least 11 pairs of flaps in total. It is difficult to distinguish lobes near the tail, making an accurate count difficult. Later studies reveal that it had 13 pairs on the trunk region and additional 3 pairs of small flaps on the neck region.