In applications such as marine rescue, marine science, archaeology, and offshore industries, autonomous underwater vehicles (AUVs) are frequently used for survey missions and monitoring tasks, with most operations being performed by manned submersibles or remotely operated vehicles (ROVs) equipped with robotic arms, as they can be operated remotely for days without problems. However, they require expensive marine vessels and specialist pilots to operate them. Scientists exploring oceans are no longer satisfied with the use of manned submersibles and ROVs. There is a growing desire for seabed exploration to be performed using smarter, more flexible, and automated equipment. By improving the field operation and intervention capability of AUVs, large-scale and long-range seafloor exploration and sampling can be performed without the support of a mother ship, making it a more effective, economical, convenient, and rapid means of seafloor exploration and sampling operations, and playing a critical role in marine resource exploration. In this study, we explored the integration technology of underwater electric robotic arms and AUVs and designed a new set of electric manipulators suitable for water depths greater than 500 m. The reliability of the key components was analyzed by finite element analysis and, based on the theory of robot kinematics and dynamics, simulations were performed to verify the reliability of the key components. Experiments were conducted on land and underwater, trajectory tracking experiments were completed, and the experimental data in air and water were compared and analyzed. Finally, the objectives for further research on the autonomous control of the manipulator underwater were proposed.