The DELTA manipulator is famous for its fast execution of tasks. This brings the ability of this robot to be used in scenarios of fast execution of tasks in an underwater environment. This capability is investigated by assigning a desired trajectory to both the underwater vehicle (UV) and the manipulator. Initially, the kinematics and dynamics of UV and DELTA are derived. Then, the forces exerted on the vehicle by the DELTA manipulator motion are considered as external interferences affecting the vehicle. Sliding mode control compensates for these external disturbances, and the vehicle follows the desired trajectory. Error in position of the UV and also the end effector is within 1 cm from the numerical analysis. The maximum actuator torques were less than 15 Nm.