How do divers' watches with buttons remain functional when in very deep water?

The pressure at 200 meters is only 284 pounds/square inch.

The buttons are very small, so that the actual pressure is not enough to compress the spring under the button.

200 meter of head = 284.394 041 265 pound/square inch

Most sports divers do not go much deeper than 30m some times 50m after that air becomes poisonous, and you will black out, at that depth you can only stay there for a few minutes. so watches of 200 meters are perfect for most divers. metal doesn't compress, so it would not be affected by the pressure, air does, but the small amount of air inside the watch, the strength of the glass, and the rubber seals, stop water from entering the watch, if you took the watch deeper than the recommended depth then probably either the seals would go or the glass would crack.

hope that helped

Most Scuba is done at a max of 30meters (100 feet) Typically you do not press buttons, you use your watch to keep track of time. Many divers are now using computers to track their dives so they know how long they can stay down and how fast they can come up.

Rubber seals and strong material.