Kaitei Daisensou

Also known has In the Hunt outside of Japan.

An organization known as the D.A.S. (The Dark Anarchy Society) uses magnetic doomsday machines to melt the polar ice caps and thus desolate the world. Although the entire world is flooded, a few societies survive to build over the highest structures they can find and continue living. In this post apocalyptic scenario, the D.A.S., who were prepared for this catastrophe, reign supreme over the survivors with martial law and military weapons of extraordinary power. Upon learning of a new D.A.S. superweapon being developed, "Yugusukyuure", the remaining survivors who are terrorized by D.A.S. secretly organize a rebellion force using a newly developed submarine known as the Granvia. The Granvia’s mission is to dive into D.A.S. enforced waters, territories and eventually the D.A.S. headquarters itself to destroy every single D.A.S. weapon in sight.