This vehicle has been conceived to be a testing bench for the development of hardware and software related with underwater robotics. Two basic principles have guided its design and development process: low-cost and modularity. The vehicle is mainly constructed with components which are either standard or which can easily be adapted to the desired purpose. The hull has been made of PVC pipe and the maneuverability is made possible thanks to four DC sealed motors, two of them placed as longitudinal thrusters. The ballast has been adjusted to give the whole structure slight positive buoyancy. Stability in roll movement is achieved placing the ballast in the lowest place and by two horizontal fins. Vertical thrusters or combining pitch and longitudinal thrust make the vehicle immerse. Bow and stern parts of the hull, where vertical thrusters are placed, are floodable. Two dry compartments occupy the central zone.