again with a piece of paper and a pencil

Thought of a submarine design. But this treats the atmosphere as a lighter form of water. A sub pumps out water and. It allows it to surface in water. If a machine could pump out leaving a void it also could "float in our atmosphere. Not quite antigravity manipulated but a more analog form to achieve a balloon with no out side chamber. Thus once air born it could then be perpelled by prop jet what ever andd guided by rudders....

Givenss water is heaviest at the bottom of the.  Ocean as air is heaviest at sea level. A sub pumps out water to surface and pumps in water to sink below the waves. Thus a ship could pump out air leaving avoid to rise above the surface and pump air back in and go back down. To the surface.     Just a thought to stimulate conversation.