The Seaview is sitting on the bottom of the ocean tilted at an angle, but the apparent angle keeps changing with different camera shots, sometimes even as the camera pans across a scene. David Hedison seems to make the greatest effort to simulate moving in a tilted submarine while other actors seem to make no effort at all at such pretense, occasionally even in the same shot.
Near the end when they counter-flooded to right the boat, from the interior camera angle indicating the subs list, they forced water into the lower side of the damaged boat allowing the boat to "right itself." In actuality it should have made the angle of the boat steeper, preventing the diving bell attaching itself to the Seaview hull.