Manipulators mounted on unmanned vehicles are inherently kinematically redundant. Such systems, which are normally controlled by operators who are far from the system, can follow a desired path both by moving its manipulator or the vehicle itself. Due to this redundancy one might control the system such that it tracks the desired path and fulfil some secondary tasks at the same time. Due to different inertia of vehicle and manipulator it is convenient to perform fast manoeuvres by manipulator and leave the vehicle uncontrolled until the manipulator reaches its physical limits or some other secondary tasks are violated. This research presents a method based on fuzzy logic for redundancy resolution of such a manipulator system during a welding mission under the sea. The method accounts for velocity disturbances induced in vehicle like submarines by environmental disturbances. It also makes it possible to prioritize secondary tasks and also the motion in different degrees of freedom of the system. In this thesis, we wish to exploit additional DOFs of the vehicle to distribute desired end-effector motion between vehicle and the manipulator. We also wish to perform fast and small motion by manipulator and slow and large motion by vehicle. Moreover, we have considered that there are normally a lot of variables for the manipulator and vehicle which are to be handled during a mission; e.g., manipulator joint angle, pitch and yaw angle of vehicle, keeping end-effector in line of sight, etc. As it can be noted handling so many parameters as secondary tasks is only possible if we use a chain of secondary tasks in a kinematic control approach. A method for kinematic redundancy resolution of such systems is presented which ensures accomplishment of the primary task and tries to fulfill a chain of secondary tasks based on their priority. The presented method can also compensate for possible motion of base due to underwater disturbances. It also makes it possible to distribute the required motion between base and manipulator and to prioritize different degrees of freedom of the base to account for inherent difficulty of control of degrees of freedom such as keeping pitch angle in a steady state different from its statistic equilibrium. Simulation results for underwater welding mission are presented to validate the proposed method.