Water Resistance - DETERMINING THE RIGHT WATCH FOR YOUR REQU

WHICH MARATHON, CWC, MWC OR OTHER MILITARY WATCH IS RIGHT FOR ME?

A lot of people ask me what they need to look for in a military watch for diving, surfing, rafting etc. Many say "150ft (50m) water resistance is enough isn't it? I won't be going down more than 75ft (25m)." I wish it was that simple but unfortunately its not. There are several important features that make a watch water-resistant. The most important is the gaskets, or 0 rings-which are made of rubber, nylon or Teflon, these form watertight seals at the joints where the crystal, case back and crown meet the case. if the watch is a chronograph, the chronograph pushers will also have gaskets and the more gaskets you have the greater the risk one might fail. In addition, water-resistant watch cases are lined with a sealant, applied in the form of a quick-hardening silicon liquid, which also helps keep the water out.

The thickness and material from which the case is made is also a big factor in determining whether a watch can safely be worn underwater. The case must be sturdy enough to withstand pressure without caving in. In general, this means a steel or titanium case. A screw-in case back, as opposed to one that pushes in, also contributes to a watch's water resistance. A screw-in crown, a feature of many divers' watches, helps prevent water getting into the case through the watch-stem hole. When it is screwed down it forms a water tight seal like the hatch on a submarine. Generally screw crowns are used when the watch is rated at water resistant to 100m/330ft or more.

Great care is needed to select the correct watch because I was horrified when I discovered that my Mil-Spec Breitling Emergency (image top right) was only 30m / 99ft rated in other words just splashproof! I has been swimming and jet skiing with it for 8 years and as a collector how I missed this is anyone's guess but luckily it never leaked and performed with exemplary reliability in every situation but nevertheless it is a really low rating for such a cutting edge watch. Needless to say it has now been sold!

Definition of Water Resistance

The various different levels of water resistance as expressed in meters, atmospheres or feet and are only theoretical. They refer to the depth at which a watch will keep out water if both the watch and the water are still. These conditions, of course, are never met in the real world. When you are swimming the movement of the wearer's arm through the water increases the pressure on the watch dramatically and this increase is even greater if you are water skiing or jet skiing; in effect this means it can't be worn to the depths indicated by lab testing machines and it is vital to select the correct watch. Personally I always opt for a minimum of 50m - the above being an exception!

Some watches are surprisingly water resistant and among them is the Marathon Chronograph below rated at 300m / 1000ft which is exceptional for a chronograph which are normally rated 50m or 100m. This is one of the mil-spec watches in my top 5.

Usage Recommendations

The following usage recommendations are suggested by most watch manufacturers and there is also some very detailed information here which sets out the technical standards in detail.

• Water-resistant to 30 meters (100 feet/3atm). Will withstand splashes of water but should not be worn in contact with water. In respect of watches made by ourselves a 30m/99ft rating normally only applies to watches that use a plexiglas or acrylic crystal and are based on 1960's (or earlier) designs where it is impractical to use a glass crystal because it would radically change the appearance of the watch.
• Water-tested to 50 meters (165 feet/5atm). Suitable for swimming in shallow water such as crossing rivers and in a pool. 
• Water-tested to 100 meters (330 feet/10atm). Suitable for swimming and snorkeling.
• Water-tested to 150 meters (500 feet/15atm). Suitable for snorkeling. 
• Water-tested to 200 meters (660 feet/20atm). Suitable for sports diving. 
• Water-tested to 300 meters (1000ft/30atm). Suitable for professional diving and military applications.
• Water-tested to over 1000 meters (3389ft/100atm). These watches have a helium escape value and are suitable for deep professional diving with mixed gases and challenging military applications.

Please Note: We do not recommend swimming or diving with your watch unless it has a screw-down crown (also known as screw-lock or screw-in crown) and is water-resistant to at least 100 meters. Many military watches which are rated at 50m/150ft are fine - be cautious with 30m or 99ft rated models such as retro designs which have acrylic crystals because these will have low water resistance like the original models in the 1960's and 70’s. There are some retro patterned watches which use an acrylic crystal which are water resistant to 50 m and also keep in mind there are some 100m variants with a glass crystal which meet modern standards whilst maintaining a retro appearance. The key is simply to know your watch.

Care of a Water Resistant Watch

It is not generally recommended to wear your water resistant watch in a hot shower, sauna or bath  because the extreme heat causes the metal parts to expand at a different rate than the rubber gaskets. This creates small openings that can allow small amounts of water to penetrate the watch. Sudden temperature changes are especially harsh if you lie in the sun and then dive into cold water.  The worst thing of all is of course a plunge pool if you've been in a sauna!

After swimming or diving in salt water, immediately rinse the watch in a stream of fresh water. If your watch has a rotating bezel, turn the bezel several times while rinsing it. This will prevent salt buildup and corrosion of the bezel ring.

Some chemicals can corrode the gaskets and make them vulnerable. Heavily chlorinated water can also cause problems, as can chlorine bleach, bath foams, sunscreen and hairsprays that work their way into the watch's seams and damage the gaskets. (They can also damage the watch's finish although this is rare with military spec watches such as CWC, Marathon, MWC, Breitling, Traser etc.)

Although fairly rare on Military Watches leather straps can be made to be water resistant too. Generally however, leather straps are easily damaged by frequent exposure to water and also start to smell and rot. So if you are going to wear your watch while swimming -- think of buying one with a metal bracelet, or a Nylon NATO strap although silicon and carbon fibre work well too.