This article presents a new application of parallel robots as underwater vehicles. The article shows the methodology applied in the design process, its modeling and the building of a novel underwater parallel robot (UPR). The designed robot is based on the well-known Stewart-Gough (S-G) platform that leads us to a new concept of geometry-variable underwater robot. The main advantage of this study is that the S-G platform allows not only a relative orientation between the two rings, but also a relative displacement, which increases the navigation capabilities of other gimbaled thruster designs. Navigation and control of this new type of underwater robots lead to new challenges that still have to be solved.