What function does a screw-down crown serve beyond aesthetics?

A screw-down crown primarily serves the function of securing the crown against water ingress. This is particularly important for watches designed to be water-resistant. When the crown is screwed down securely against the case, it creates a tight seal, preventing water from entering the watch's inner mechanisms, which can damage components and affect its functionality.

Models designed for diving or other aquatic activities often utilize this feature to ensure reliability under water pressure. The engineering of such crowns is a critical element in enhancing a watch's durability and performance in challenging conditions. The aesthetic aspect may enhance the look of the watch, but the primary benefit relates to its practicality and protection against environmental elements.