A new underwater robot arm was developed through intensive cooperation between different academic institutions and an industrial company. The manipulator, which was initially designed to be teleoperated, was adapted for our autonomy needs. Its dimensions and weight were reduced, and its kinematic model was developed so that autonomous control can be performed with it. We compare several commercially available underwater manipulators and describe the development of the new one, from its initial configuration to its mechanical adaptation, modeling, control, and final assembly on an autonomous underwater vehicle (AUV). The feasibility and reliability of this arm is demonstrated in water tank conditions, where various innovative autonomous object-recovery operations are successfully performed, both in stand-alone operation and integrated in an AUV prototype.