The mechanical design, construction, operation and initial performance of a prototype innovative dextrous underwater end effector are described. The three-fingered hydraulic device utilizes continuously flexible fingers to perform grasping and manipulation. Finger movements are produced by the elastic deformation of bellows elements due to internal pressure. A single degree of freedom knuckle joint at the base of each finger enables the device to be used across a wide range of object sizes. A comparison between theoretical and actual non-contact movements for this type of flexible finger is also included.