Submarine activities have increased steadily in the last forty years all over the world. In Brazil, many unmanned underwater vehicles have been used in delicate, precise and risky tasks in the oil industry. Due to strategic economical interest, a Semi-Autonomous Underwater Vehicle (SAUV) is being developed at the Univ. of São Paulo (USP). This work presents the development of a Robust Control System, which will be embedded in the SAUV. The controller synthesis is based in a Tracking System fed by a State Estimator. The controller is able to keep the vehicle in a desired trajectory and also shows very good performance in activities involving Dynamic Positioning. To develop the controller, an interactive methodology was used, until a satisfactory performance level was reached, involving three main activities: modeling of the SAUV, controller synthesis and simulations of operation under normal and abnormal conditions. This work was written as partial fulfillment of requirements to obtain the MSc degree in Control Eng. at the Polytechnic School of USP, and it is now published worldwide to offer a contribution to scientific and industrial communities.