The history of actual water-resistant watches began in the 1920s, but it came into existence not until later than that period. Nowadays dive watches are the most popular type of sports watch, not because of diving purposes, but because of their style, the promise of durability, and utilitarian value.
The first men’s wristwatches were created from pocket watches which had lugs soldered onto their cases. The issue for soldiers of the late 1800s and then of World War was wristwatches were notoriously poor reliability: they were prone to breaking as they were exposed to a significantly greater amount of shocks, humidity and temperature changes when worn on the wrist and not inside the pockets of coats and vests
Water, humidity, and dust would make components rust, cause lubricants to not function as they should and ultimately force gears and pinions to lock up and springs to deteriorate. So, if watches were to be worn on the wrist, giving them much greater exposure to these elements, there was some remodeling to be considered and manufactured so as the assembling process. Therefore, engineers proposed a small round-cased watch with a chunky external case around it, which had a “lid” that would screw onto it. It worked like a sealed jar.
This made sense here as there were no properly developed crown sealing systems and the lid covered that as well. The problem this created was that every time the hand-wound movement was to be rewound or the time needed to be set, the lid had to be removed and then put on again.
The frequent use meant that the grooves on the side of the brass lid and the threads on the inside of it wore out quickly, necessitating repairs. A more practical and more durable solution was to comprise a threaded ring that would go around the movement and bezel, and the case back would be screwed onto the outer, threaded surface of this ring. This resulted in a superior seal, without having to use a chunky external cover.