A screw-down crown is a watch crown that threads onto the case tube like a screw, sealing the watch tightly shut. It's the standard for dive watches and any watch built for serious water resistance.
How it works
A normal crown just pushes in and relies on gaskets to hold back water. A screw-down crown adds threads: you press it toward the case and turn it until it locks down, compressing the gaskets for a much tighter seal. To set the time, you unscrew it first — turn counterclockwise until it pops free, then pull it out as usual.
Why it matters for water resistance
The crown is the most vulnerable opening in a watch case. Screwing it down is what lets dive watches hit high water resistance ratings and stay sealed under pressure. A pushed-in crown can be knocked loose; a screwed-down one stays put. That's why nearly every watch rated for real diving uses one.
Using it right
Two rules. First, always screw the crown fully back down after setting the time — a crown left unscrewed offers little protection, even on a dive watch. Second, never force it. If the threads resist, back off and start again so you don't cross-thread them. Cross-threading is a common, avoidable way to wreck a crown.