Pressure hulls are, especially for manned vehicles, one of the key structures of a submarine. Contributing roughly one third to the total submarine weight, these hulls provide a watertight envelope that must bear the hydrostatic external load. The design of such a structure can be complex as the whole submarine has to reach neutral buoyancy. Hence, the addition of structural hydrostatic load bearing capacity is not a straightforward operation. Increase of structural weight is not an option as it decreases the weight budget of the payload, engine and other performance related features. Obviously, the use of a lightweight pressure hull opens the door to a performance increase. In the search of a lightweight pressure hull, it is found that use of composite materials can be a solution. However, a composite pressure hull design encapsulates the design of the composite itself. For this reason, pressure hull finite element models are created that include the composite related material mechanics. Suitable weight minimization techniques are performed on these models and results were compared to the conventional heavyweight pressure hull. As a result, it is demonstrated that pressure hulls made of sandwich-constructed composite offer a promising weight reduction of 28% with respect to the conventional reference design.