A diving watch
is a watch
designed for underwater diving
that features, as a minimum, a water resistance
greater than 10 ATM
, the equivalent of 100 meters (330 feet). The typical diver's watch will have a water resistance of around 200 - 300 meters (660 - 990 feet), though modern technology allows the creation of diving watches that can go much deeper. A true diver's watch is in accordance with ISO 6425
, which defines test standards and features for watches suitable for diving with underwater breathing apparatus in depths of 100 m or more. Watches conforming to ISO 6425 are marked with the word DIVER'S
to distinguish diving watches from look a like watches that are not suitable for actual scuba diving.
Early dive watches were often developed in response to military
and professional needs. Omega SA
probably deserves the honour of having created the world's first diving watch, with the Omega "Marine," introduced in 1932.
As supplier to the Royal Italian Navy, Panerai offered underwater timepieces in the 1930s, which were not only waterproof at 650 feet, but luminescent as well.
In addition, a large number of "canteen" style dive watches by Hamilton, Elgin or Waltham were made to military specification during and after WWII. However, these watches were made in small numbers, and were not intended for large-scale commercial distribution. Today, interest in these watches is limited to collectors.
In 1953 Lip-Blancpain's Fifty Fathoms waterproof watch came on the market in France. Various models were issued by Blancpain in small quantities to the military in several countries, including US and French Navy combat diver teams. The fifty fathoms was worn by Jacques Cousteau and his divers during the underwater film "Le monde du silence", which won the Palme d'or at the Cannes film festival in 1956, and in the US when TV star Lloyd Bridges wore a Blancpain Fifty Fathoms dive watch in a photo that appeared on the cover of the February 1962 edition of Skin Diver Magazine.
The Rolex Submariner was introduced at the Basel Watch Fair in 1954 which coincided with the development of self-contained underwater breathing apparatus, known as scuba. In 1961 Rolex began to include a skindiver handbook with the Submariner, then available in two models, one water resistant to 200 meters/660 feet, the other, less expensive version, to 100 meters/330 feet. It was the choice of watch for the character of 007 in the first ten James Bond films, causing the "Sub" to achieve an iconic status.
During the 1960s commercial work in the oceans and seas created professional diving organisations that needed tool watches designed for conducting safe diving operations at greater depths. This lead to the development of the first 'ultra water resistant' watches like the Rolex Sea-Dweller Submariner 2000 (2000 ft = 610 m) that became available in 1967 and was produced in several variations and the Omega Seamaster Professional 600m/2000ft also know as the "Omega PloProf" (Plongeur Professionel) that came available in 1970.
The vast majority of divers now use electronic, wrist-worn dive computers by manufacturers such as Suunto, Uwatec, Mares, Pelagic and Seiko. Diving watches are however still commonly used by divers as a back-up instrument for overcoming dive computer malfunctions.
Many contemporary sports watches owe their design to diving watches.
Many companies offer highly functional diving watches. Whilst diving watches are primarily tool watches, some companies offer models that can in addition to this be regarded by some as jewellery or fine mechanical devices. Diving watches can be analog or digital.
ISO 6425 standard for diving watches
The standards and features for diver's watches are regulated by the International Organization for Standardization
in the ISO 6425
standard. Besides water resistance standards to a minimum of 100 meter depth rating ISO 6425 also provides minimum requirements for mechanical diver's watches (quartz and digital watches have slightly differing readability requirements) such as:
- The presence of a unidirectional bezel with at least at every 5 minutes elapsed minute markings and a pre-select marker to mark a specific minute marking.
- The presence of clearly distinguishable minute markings on the watch face.
- Adequate readability/visibility at 25 cm (9.84 in) in total darkness.
- The presence of an indication that the watch is running in total darkness. This is usually indicated by a running second hand with a luminous tip or tail.
- Magnetic resistance. This is tested by 3 expositions to a direct current magnetic field of 4,800 A/m. The watch must keeps its accuracy to +/- 30 seconds/day as measured before the test despite the magnetic field.
- Shock resistance. This is tested by two shocks (one on the 9 o'clock side, and one to the crystal and perpendicular to the face). The shock is usually delivered by a hard plastic hammer mounted as a pendulum, so as to deliver a measured amount of energy, specifically, a 3 kg hammer with an impact velocity of 4.43 m/sec. The change in rate allowed is +/- 60 seconds/day.
- Chemical resistance. This is tested by immersion in a 30 g/l NaCl solution for 24 hours to test its rust resistance. This test water solution has a salinity comparable to normal seawater.
- Strap/band solidity. This is tested by applying a force of 200 N to each springbar (or attaching point) in opposite directions with no damage to the watch of attachment point.
- The presence of an End Of Life (EOL) indicator on battery powered watches.
The watch cases of diving watches must be adequately water(pressure) resistant and be able to endure the galvanic corrosiveness
of seawater, so the cases are generally made out of materials like stainless steel
and synthetic resins
. The case must also provide an adequate degree of protection against external magnetic
influences and shocks, though diver's watches do not have to be able to endure strong magnetic fields and shocks. To make mechanical watch movements themselves shock resistant various shock protection systems
can be used.
Elapsed time controller
Analog diving watches will often feature a rotating bezel
, that allows for an easier reading of elapsed time from a specific point. This is used to compute
the length of a dive. (See Tachymeter
.) The bezel can be turned so the wearer can align the zero on the bezel with the watch's seconds or minute’s hand. After a period of time passes, the elapsed time can be read off the bezel. This saves the wearer having to perform the subtraction that would be necessary if the watch's regular dial was used. It is also much easier to read this larger dial while underwater. On diving watches the bezel is "unidirectional", i.e. it contains a ratchet so it can only be turned anti-clockwise to increase
the apparent elapsed time. If the bezel could be turned the other way this could suggest to a diver that the elapsed time was shorter than the truth, which could be highly dangerous. 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.
Most contemporary dive watches with conspicuous 15 or 20 minute markings on their bezels, are the result of copying a Rolex bezel design of the 1950s. Back then divers typically planned a dive to a certain maximum depth based on now obsolete US Navy dive tables
, and dove according to the planned dive profile. If the dive profile allowed a bottom time of 35 minutes the diver, upon entering the water, would set the marker on the bezel, 35 minutes ahead of the minute hand. The diver calculated this with the 60 - bottom time formulae (60 - 35 = 25, for 35 minutes bottom time the diver would align the 25 minute bezel-mark with the minute hand). Once the minute hand reached the main-marker on the bezel the diver would begin his ascent to the surface. The 15 or 20 minute scale helped with timing the ascent and whatever safety stop the diver deemed necessary. For contemporary diving methods the 15 or 20 minute "count-down" bezel is quite antiquated.
Diving watches have relatively thick watch crystals. Sometimes domed crystals are used to enhance the pressure resistance of the watch. The typical materials used for crystals are acrylic glass
, hardened glass
and (synthetic) sapphire
which all have their pros and cons. Acrylic glass is very break resistant but can easily be scratched. It has however the advantage small scratches can be buffed out with polishing compounds. Hardened glass is more scratch resistant than acrylic glass and less brittle than sapphire. Sapphire is very scratch resistant but less shatter proof than the other crystal options. Anti-reflective coatings are generally applied on sapphire crystals to enhance the legibility of the watch. Some manufacturers use sapphire/hardened glass laminate
crystals, where the scratch resistance sapphire is combined with the better shatter resistance of hardened glass.
Analog diving watches must have a water resistant crown. Often the crown has to be unscrewed to set or adjust the time and date and afterwards retightened to restore the water resistance of the watch and minimize the chance of unintentional operation under water. 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.
Digital and some analog chronograph
diving watches - such as the
Avenger Seawolf Chronograph, Doxa
Aquatimer Minute Memory, the Omega
Seamaster Professional Chrono Diver series and Sinn
U1000 - have specially-designed push pieces that can be operated at depth without allowing water to enter the case.
Helium release valve
Some diving watches intended for saturation diving
at great depths are fitted with a helium
or mixed breathing gas release or escape valve
to prevent the crystal from being blown off by a pressure build up caused by helium that has seeped into the watch in helium enriched environments as the watch and diver adjust to normal atmospheric conditions. Other helium safe/for mixed-gas rated diving watches can withstand the helium used in certain diving situations by using gaskets that simply do not allow helium gas to enter the watch case in a harmful way in the first place.
Most diving watches feature a rubber, silicone rubber or polyurethane strap or a metal bracelet of adequate length to facilitate wearing the watch over a diving suit sleeve. For this bracelets often have a (concealed) Divers extension deployment clasp by which the bracelet can be appropriately extended. One piece (NATO style) nylon fabric straps that slide under the watch case through both springbars are used to minimize the chance of losing the watch due to a springbar failure.
The dials and markers on the watch face and bezel have to be legible under water and in low light conditions. An indication that the watch is running in total darkness also has to be present.
For easy legibility most diving watches have high contrasting, none cluttered dials and markers with a large, easily identifiable minute hand. The markers for 3, 6, 9 and (especially) 12 o'clock on the watch face and the zero marker on the bezel of analogue diver's watches are usually conspicuously styled to prevent disorientation induced read out errors.
For low light conditions luminous phosphorescent non-toxic strontium aluminate based lume pigments marketed under brand names like Super-LumiNova or NoctiLumina and tritium based self-powered lighting devices called "gaseous tritium light source" (GTLS) is applied on the dials and markers. On digital diving watches lightened displays are used for low light conditions legibility.
Power reserve indicator
A diving watch with an electric battery powered movement must have an End Of Life (EOL) indicator, usually in the form of a two or four second jump of the second hand or a warning message on a digital display to safeguard against insufficient power reserve during underwater activities. Some electric and mechanical powered movement models have power reserve indicators that show the current power status of the watch. Mechanical movements should be wound or in case of automatic movements given enough motion before a dive.
The International Organization for Standardization issued a standard for water resistant watches which also prohibits the term waterproof to be used with watches, which many countries have adopted.
Water resistance is achieved by the gaskets which forms a watertight seal, used in conjunction with a sealant applied on the case to help keep water out. The material of the case must also be tested in order to pass as water resistant.
None of the tests defined by ISO 2281 for the Water Resistant mark are suitable to qualify a watch for scuba diving. Such watches are designed for everyday life and must be water resistant during exercises such as swimming. They can be worn in different temperature and pressure conditions but are under no circumstances designed for scuba diving.
The standards for diving watches are regulated by the ISO 6425 international standard. The watches are tested in static or still water under 125% of the rated (water)pressure, thus a watch with a 200 meter rating will be water resistant if it is stationary and under 250 meters of static water. The testing of the water resistance is fundamentally different from non-dive watches, because every watch has to be fully tested.
ISO 6425 water resistance testing of a diver's watch consists of:
- Immersion of the watch in 30 cm of water for 50 hours.
- Immersion of the watch in water under 125% of the rated pressure with a force of 5 N perpendicular to the crown and pusher buttons (if any) for 10 minutes.
- Immersion of the watch in 30 cm of water at the following temperatures for 5 minutes each, 40°C, 5°C and 40°C again, with the transition between temperatures not to exceed 1 minute. No evidence of water intrusion or condensation is allowed.
- Immersion of the watch in a suitable pressure vessel and subjecting it to 125% of the rated pressure for 2 hours. The pressure must be applied within 1 minute. Subsequently the overpressure shall be reduced to 0.3 bar within 1 minute and maintained at this pressure for 1 hour. No evidence of water intrusion or condensation is allowed.
- For mixed gas diving the watch has to be immersed in a suitable pressure vessel and subjecting it to 125% of the rated pressure for 15 days in a (helium enriched) breathing gas mix. Subsequently the overpressure shall be reduced to normal pressure within 3 minutes. No evidence of water intrusion, condensation or problems caused by internal overpressure are allowed.
- An optional test originating from the ISO 2281 tests (but not required for obtaining ISO 6425 approval) is exposing the watch to an overpressure of 2 bar, no more than 50µg/min of air is allowed to get inside the case.
Except the thermal shock resistance test all further ISO 6425 testing should be conducted at 18 to 25°C temperature.
The required 125% test pressure provides a safety margin against dynamic pressure increase events, water density variations (seawater is 2 to 5% denser than freshwater) and degradation of the seals.
Movement induced dynamic pressure increase is sometimes the subject of urban myths and marketing arguments for diver's watches with high water resistance ratings. When a diver makes a fast swimming movement of 10 m/s (32.8 ft/s) (the best competitive swimmers can not nearly swim that fast) physics dictates that the diver generates a dynamic pressure of 0.5 bar or the equivalent of 5 meters of additional water depth.
Water resistance classification
Watches are classified by their degree of water resistance, which roughly translates to the following (1 meter = 3.2808398950131 feet):
| Water resistance rating
|| Remarks |
| Water Resistant 30 m or 50 m
|| Suitable for water related work and fishing.
|| NOT suitable for swimming or diving. |
| Water Resistant 100 m
|| Suitable for recreational surfing, swimming, snorkeling, sailing and water sports.
|| NOT suitable for diving. |
| Water Resistant 200 m
|| Suitable for professional marine activity and serious surface water sports.
|| NOT suitable for diving. |
| Diver's 100 m
|| Minimum ISO standard (ISO 6425) for scuba diving at depths NOT requiring helium gas.
|| Diver's 100 m and 150 m watches are generally old(er) watches. |
| Diver's 200 m or 300 m
|| Suitable for scuba diving at depths NOT requiring helium gas.
|| Typical ratings for contemporary diver's watches. |
| Diver's 300+ m for mixed-gas diving
|| Suitable for saturation diving (helium enriched environment).
|| Watches designed for mixed-gas diving will have the DIVER’S WATCH L M FOR MIXED-GAS DIVING additional marking to point this out. |
Note: The depth specified on the watch dial or case represents the results of tests done in the lab, not in the ocean.
Some watches use bar instead of meters, which may then be multiplied by 10 to be approximately equal to the rating based on meters. Therefore, a 20 bar watch is equivalent to a 200 meter watch. Some watches are rated in atmospheres (atm), which are roughly equivalent to bar. In the United Kingdom, scuba divers and others often use the word atmosphere (ATM) loosely (the correct term is "ambient pressure") to mean 1 bar (1000 millibars, or 100 000 Pa).
Watches designed for extreme water resistance
The design and actual availability of diver's watches certified for more than 1,000 meters (3,281 ft) is not solely explicable by practical diving needs. The diving depth record for actual off shore diving was achieved in 1988 by a team of professional divers
of the Comex S.A. industrial deep-sea diving
company performing pipe line connection exercises at a depth of 534 meters of seawater (MSW) (1752 ft) in the Mediterranean Sea
. The diver's watches used were Rolex Sea Dwellers
that are the standard issue diving watch for every Comex diver since 1976. In 1992 a Comex diver achieved a record of 701 MSW (2300 ft) in an on shore hyperbaric chamber
. The watch used during this scientific record dive, where a hydrogen-helium-oxygen gas mixture was used as breathing gas
, was a Rolex Sea Dweller 4000 that has a 1220 meters (4000 ft) water resistance rating. The complexity and accompanying high costs of professional diving to extreme depths and the development of deep water atmospheric diving suits
and remotely operated underwater vehicles
in offshore oilfield drilling and production effectively nixed the need for ever deeper non-atmospheric manned intervention in the ocean.
The cases of some diver's watches designed for extreme depths are filled with silicone oil exploiting the virtual incompressibility of liquids. An example of these watches is the Sinn UX (EZM 2B) which case is certified for 12,000 meters (that’s deeper than the Challenger Deep), however, the quartz controlled movement can only withstand 5,000 meters. This technology only works with quartz movements as a mechanical movement does not work properly in the oil filled case. An advantage of this technology is that the time can be read very well under water.
Most manufacturers recommend divers to have their diving watch pressure tested by an authorized service and repair facility annually or every two to three years and have the seals replaced. Besides that simple maintenance by the owner is also important. Most manufacturers recommend rinsing the watch in fresh water after use in seawater, but leaving a diver's watch in fresh water overnight is a good method to protect the watch from corrosion and to keep the crown, buttons and pressure sensors on digital ones working. Divers also have to inspect their watch and wrist band for defects before every dive and especially in case it came into contact with gasoline or strong chemicals, powerful magnetic fields or was banged against something hard during use.