This paper presents the dynamic modeling of a 3-D-serial underwater ee1-like robot using recursive algorithms based on the Newton-Euler equations. Both direct and inverse models are treated in the paper. The inverse dynamic model algorithm gives the head acceleration and the joint torques as a function of the joint positions, velocities, and accelerations. The direct dynamic model gives the head and joint accelerations as a function of the joint positions, velocities, and input torques. The proposed algorithms can be considered as a generalization of the recursive Newton-Euler dynamic algorithms of serial manipulators with fixed base. The algorithms are easy to implement and to simulate whatever the number of degrees of freedom of the robot. An example with 12 spherical joints is presented. The fluid forces have been taken into account using a simple model based on Morison's model.