Question

what can a submarine do that a regular boat cant?
dive beneath the surface of the ocean
hover over the surface of the ocean
submit

Explanation:

Regular boats operate on or above the ocean's surface, unable to submerge below it. Submarines are designed to travel underwater, which is a unique capability compared to standard boats. Hovering over the surface is something regular boats can do (by floating), so it is not the distinct action.

Answer:

dive beneath the surface of the ocean