This has been a old live-action movie from Asia, most likely Japan. I've seen it some time in the late 80's and I think it's been black/white only.
Earth is invaded by UFOs (small and round, like flying balls), coming from Mars.
Japan (I think) built some kind of super spaceship, initially hidden within some secret port in some kind of island/mountain.
The spaceship looks similar to a classic battleship, but with an added drill below the front.
In the movie's finale it's revealed that this is some kind of
super weapon/bomb that has to be manually piloted by someone. When launched it starts rotating and flies (formed like a bullet but with the drill/corkscrew head).
To defend Earth, the ship is sent on a mission to Venus, where the UFOs seem to originate. I don't remember the specific reason or conclusion here.
The ship starts underwater or launches from the mountain on the island, then taking off and fighting UFOs while leaving Earth's atmosphere.