The Hydro Sub is a new design for submarines that will reduce the cost of making the submarines, reduce the weight of the submarine itself, while at the same time increasing its strength. This would enable faster production times and using less materials. In the water it would be able to move easier while requiring less fuel.
It is a simple law of physics that you cannot compress a liquid! Metals, no matter how strong, at a certain depth the pressure is to great and the vessel can implode.
This idea requires much less metal but two layers of thinner material that can best be described as a submarine inside of a submarine. In between these two layers of metal would be filled completely with liquid, most likely purified water.
Since you cannot compress a liquid, this layer of liquid would dramatically increase the strength of the submarine. This would also increase the buoyancy of the vehicle creating a lighter submarine.
The result would be easier manufacturing, cheaper cost, have heavier payloads and an overall lighter submarine that would cost less to operate.