When buying a divers watch there can be many features that are different between manufacturers,the list here are some of the features that you will find on a typical divers watch.
Watch Case
The watch cases of diving watches must be adequately water and pressure resistant to with stand the forces when there under water and be able to endure the corrosiveness of seawater, so the watch cases are typically made out of materials such as stainless steel, titanium, ceramics and synthetic resins or plastics. The case must also provide protection against external magnetic influences and shocks.
Elapsed time controller
Analog diviers watch will often feature a rotating bezel, which is used to read elapsed time from a specific point. This is used to compute the length of a dive. The bezel is used by turning until you can align the zero on the bezel with the watch's seconds or minute’s hand. As time elapses the reading can be read of the bezel. This will save the scuba diver from having to perform the subtraction that would be necessary if the watch's regular dial was used and the plus of having a bg dial to read when underwater. On a divers watch the bezel is "unidirectional", meaning the bezel can be turned in a single direction as turning it the wrong way can so not to increase the length of time under water. So the bezel can only move in a way that will give a shortened time underwater. Digital dive watches usually perform this function by use of a standard stop watch function. Digital dive watches may also feature a depth gauge and logging features.
Strap/bracelet
Generally a divers watch features a rubber, silicone rubber or polyurethane strap or a metal bracelet of adequate length to allow the waering of awet or dry suit. For this bracelets often have a (concealed) Divers extension deployment clasp by which the bracelet can be appropriately extended.
Bezel Markings
Most contemporary dive watches with conspicuous 15 or 20 minute markings on their bezels, are the result of copying a Rolex bezel design back from the 1950s. Back then divers typically planned a dive to a certain maximum depth based on US Navy dive tables, and dove according to the planned dive profile.
Crown
The typical analog divers watch must have a water resistant crown else it would flood. Often the crown has to be unscrewed to make any adjustments to the time and date and afterwards retightened to restore the water resistance of the watch. There are however models that have crowns that are operated like the crowns of non diver's analog watches. Screw down locking crowns and traditionally operated water resistant crowns can not be operated under water.
