| The degree of water resistance needed in a watch | | | | crystals; extraordinary precision of machined parts; gas |
| depends entirely on how it's going to be used. If it won't | | | | filling; pressure venting; and various other methods. |
| be immersed to any appreciable depth, then minimal is | | | | Many of these features aren't easily discernable, |
| fine, but if you're considering it for swimming or diving, | | | | however a couple are easy enough to observe |
| then something more substantial is required. | | | | visually. First is a case-back that screws down into the |
| Depth ratings for the amount of water-resistance vary | | | | case against a rubber or synthetic seal. Look for |
| from about 30 meters (100 feet) to 1000 meters (3300 | | | | notches around the case-back that are the leverage |
| feet) and more. The point to remember about them is | | | | points for the jewelers tool used for this purpose. |
| that the rating determination is done under controlled | | | | Secondly, the crown should screw in against a similar |
| conditions in a test lab and rarely reflects the real | | | | seal, thus locking down the stem. |
| world. For instance, in a lab, the watch isn't being | | | | Another factor is the case material. For diving, it should |
| moved or bumped, nor is the water temperature | | | | be stainless steel or titanium. Some polymer cases will |
| varied. | | | | work if rated to an appropriate depth. Other materials |
| Generally speaking, a depth rating of less than 100 | | | | including gold don't work well because they aren't rigid |
| meters (330') means the watch can be worn in the | | | | enough to withstand pressure at depth. Just a slight |
| rain, or will be okay if splashed. Ratings greater than | | | | flexing can allow water to seep in around a seal. |
| 100 but less than 200 meters (660') mean the watch | | | | Finding a watch that can just get wet is easy enough, |
| can be used swimming or for shallow dives, like | | | | but finding one that can survive the rigors of scuba |
| snorkeling. For scuba diving you need a rating of 200 | | | | diving requires more scrutiny. As mentioned above |
| meters or greater. | | | | there are several features that contribute to |
| Obviously for deep diving, including everything from | | | | maintaining the water-tight integrity of a watch, many |
| technical to commercial or saturation diving, the depth | | | | of which aren't so observable. |
| rating should be at the high end and preferably to an | | | | The best way to be certain, after visual observation, |
| appropriate ISO Standard. | | | | and a review of the manufacturers specs, is to |
| Manufacturers make watches water resistant to | | | | choose one with a sufficient depth rating. If recreational |
| varying degrees through application of sealants inside | | | | scuba diving is the intended use, then it's reasonable to |
| the case; use of o-rings and gaskets of rubber or | | | | infer that a watch with the deeper depth rating of 200 |
| some synthetic material to seal all joints; extra-thick | | | | meters (660 feet) or more will meet your needs. |