The optical phenomenon you are describing, where ships appear to sink bottom-first over the horizon but can be seen again with the aid of telescopes or zoom lenses, is a result of the Earth's curvature and the limitations of human vision.
The Earth is a curved surface, and as a result, the horizon—the line where the sky appears to meet the Earth—appears curved as well. When an object such as a ship moves away from an observer towards the horizon, it gradually becomes obscured by the curvature of the Earth.
As the ship moves farther away, the bottom part of the ship is hidden by the curvature first because it is closer to the surface of the Earth. This creates the illusion that the ship is sinking bottom-first over the horizon, even though it is actually just being obstructed by the Earth's curvature.
However, the ability to see the ship again with the aid of telescopes or zoom lenses is due to the magnification and increased resolving power of these optical instruments. They allow us to overcome the limitations of human vision, which can't resolve small details or discern objects at long distances as effectively.
Telescopes and zoom lenses can bring distant objects, such as ships, back into view by magnifying the image and allowing us to see details that were previously too small or too far away to be resolved by the naked eye. This is why the ships reappear fully visible when observed through these optical devices.
In summary, the apparent sinking of ships over the horizon is an optical illusion caused by the curvature of the Earth. The use of telescopes or zoom lenses enables us to see the ships again by magnifying the image and overcoming the limitations of human vision.