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Underwater operation and sampling has been replaced by ROV (Remotely Operated Vehicle) and underwater manipulator gradually, which can avoid divers to face the dangers due to the environmental pressure and low temperature. When ROV to carry out the mission, the operator sees the undersea environment and the target with the information feedback from the sensors. Recently, we developed a general purpose controller for controlling underwater robotic systems. We plan to install the manipulator on the ROV with the same general purpose controller. One of the concerns in desgining is: the ROV generally mantains neutral buoyant in seawater. When adding or removing any components, the arrangement of balast weight needs to done again to keep the balance of the system. Moreover, the center of gravity will be changed such that dynamics of the ROV will be different when collaborating with the underwater manipulator. To resolve these problems, we review the design and hope to reduce the size and weight of each component.The new design also introduces the use of a junction box. The junction box keeps all the circuits, power converters and motor control card. It allows the reconfiguration of power and commands pathway much easier. To reduces of the size of the housings, the gear transmission set is moved out of the housing. According to the positioning accuray requirement of each axis, a DC servomotor or a DC motor is installed. Underwater manipulators do not require agile motion. Therefore we use a gear-worm set as the transmission between links to increase torque. The motion control is implemented with a Jacobian to calculate the increment joint angles for joint coordinate control. Human-interface was developed with Borland C++ Builder and OpenGL to let the operator to simulate and control of the manipulator with an input of a 3D joystick.