Atmospheric pressure

There are many types of watches that perform specific tasks. There are aviator watches, fashion watches, but most importantly there are diving watches. One of the most popular diving watches, The Rolex Submariner, is a timeless piece that many watch collectors begin with. The watch face details the depth that it can go under water. As you can see in the diagram, the watch can be submerged 4,000 ft. in water and still function. Many diving watches will have this indication on the face with some at varying levels. This means that these watches can stand both the atmospheric pressure and the additional pressure of being submerged in water.
The further you go down, the higher the force of pressure is on you. This is due to the larger volume of water above you as well as the atmospheric pressure weighing down. Diving watches were made with these environments in mind in order to still function and provide accurate measurements. ​

A diagram of atmospheric pressures under water. idc-guide.com

The face of a sea-dweller Rolex diving watch. bobswatches.com