 This paper presents a new type of robot inspired by the motion of a moon jellyfish. It uses a contraction-expansion mechanism to achieve a maximum vertical swimming speed of 7.3 millimeters per second and is characterized by a simple design. The robot, called GelaZ, utilizes a contraction-expansion mechanism for swimming similar to the motion of a moon jellyfish. This paper investigates the characteristics of this motion, including fluid structure interaction and vortex formation, and compares them to those of other GelaFish-inspired robots. The results show that the robot's swimming metrics are comparable to those of other GelaFish-inspired robots, but its actuators are more scalable and easier to make than those used in other designs. This article was authored by Pawandeep Singh Mathuru, Penya O'Gong, Koti Pramod Reddy Guntaka, and others.