What is a consequence of not properly winding a watch?

When a mechanical watch is not properly wound, a primary consequence is that the movement may stop working. Mechanical watches require a certain amount of energy to keep their gears and mechanisms in motion. This energy usually comes from a mainspring that is wound either manually or automatically through the motion of the wearer's wrist.

If the watch is not wound sufficiently, the mainspring may lose its tension and eventually run down completely. Once the mainspring is unwound, the movement ceases to operate, which results in the watch no longer keeping time accurately or at all. Therefore, failing to properly wind a mechanical watch directly impacts its ability to function, validating that this consequence is significant for maintaining the watch's operation.

Other choices do not align with the functionality of a watch. For example, a watch cannot become waterproof simply due to insufficient winding, nor does the state of winding directly affect battery life in quartz watches. Additionally, the time displayed cannot improve from being unwound; in fact, it would result in a failure to display time altogether.