This paper reports analysis and simulation studies for the coordinated control of multiple manipulators on a free swimming under water robot. The control objective is to perform an open loop control of the position of end-effector of the mission arm. The authors derive the formulation for inverse dynamics as well as inverse kinematics of an underwater robot with multiple manipulators, having a redundancy of degrees of freedom (DDF) of motion, in the presence of external generalized forces. The method is applied to a model of underwater robot installing a 6 DOF mission arm and a pair of 2 DOF paddling arms used for stabilization in a free swimming condition. The numerical simulation results show the effectiveness of the presented coordinated control method with the assistance of the stabilizing arms.