A dive watch reflects a sense of adventure and intrigue with visions of exploring the deepest and darkest depths of oceans and underwater caverns. As diving has become more popular, with inspiration drawn from the past achievements on TV of Jacque Cousteau and his Calypso in the 1960s and 70s, diving has become safer and more accessible, leading to a boom in the popularity of dive watches. Beyond their use as serious underwater tools, dive watches have become symbols of exploration and masculinity. The history of the dive watch dates back to Omega SA who was credited as the creator of the world’s first industrially produced diving watch, the Omega “Marine”, which was introduced in 1932.
Basically there is three types of dive watches: digital, classic (mechanical or analog models), and the dive computer.
What is a dive watch?
To be defined as a proper dive watch, it has been regulated by the standards and features in the International Organization for Standardization (ISO 6425 standard), which requires a minimum of 100m depth (330ft) rating and possessing a system to control the time. The ISO 6425 requirements are:
A time-preselecting device or a unidirectional bezel (which secures the glass or crystal on the face of the watch), or a digital display and computes how long you have been submerged. The bezel shows the elapsed time underwater so that if knocked by accident, a diver can only surface earlier not later. It’s a fail-safe feature to protect the diver. The bezel should have a 5-minute marking scale up to 60 minutes. Bezels are used in analog divers watches. Digital dive watches usually perform this same function by use of a standard stopwatch function. Digital dive watches may also feature a depth gauge and logging features, but are not usually regarded as a substitute for a dedicated dive computer.
1. Water resistance
Watches are tested in static or still water under 125% water pressures. A watch with a 200m rating is water-resistant if it has been stationary in less than 250m of static water, so it’s not the depth that is important here but the pressure on the watch. Dive watches therefore which are marketed as resistance in 100m, 200m, etc can be misleading. Watch manufacturers tend to relate bars of pressure with meters, with 10 bar equating to 100 meters, 20 bar to 200 meters, etc.
The presence of an End of Life (EOL) indicator on battery-powered watches; an indication the watch is running; and visibility at 25cm (9.8 inches) in total darkness.
3. Anti-magnetic resistant
This is tested by 3 exposures to a direct current magnetic field of 4,800 A/m. The watch must keep its accuracy to +/- 30 seconds/day as measured before the test despite the magnetic field.
4. Shock resistant
This is tested by two shocks delivered at different locations on the watch. 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/s. The change in rate allowed is +/- 60 seconds/day.
5. Resistance to chemicals (salty water)
This is tested by placing the watch in a saltwater solution (30g/l NaCl) for 24 hours at 18⁰C-15⁰C to test for rust resistance.
6. Strap/band solidarity
It contains a band that is resistant to external forces (tested by applying a force of 200N (45lb) to the band). To endure corrosiveness of the saltwater most dive watches have a rubber, silicone rubber, polyurethane, or a stainless steel watch strap.
The watch is placed on a heated plate at a temperature between 40-50⁰C until the temperature of the watch is the same as the plate. A drop of water (18-25⁰C) is placed on the glass of the watch, and after 1 minute the glass is wiped. Any watch with condensation on the interior of the glass is eliminated.
Conforming watches are marked as a diver watch (i.e. “Divers Watch L M” or “Divers L M”). This distinguishes lookalike watches not suitable for scuba diving. The letter ‘L’ indicates the diving depth in meters.
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Dive Watch Crystal
The watch crystal is the transparent cover over the face of the watch. Usually, there are three types of watch crystals: plexiglass (plastic or acrylic); mineral glass; and sapphire crystals.
Plexiglass is the cheapest, but most likely to get scratched, and least likely to shatter.
Mineral crystals are like ordinary glass that is used in windows. They are more scratch-resistant than plexiglass, but also more likely to shatter (but not break).
A better more durable watch will have a thicker sapphire crystal which is more expensive but more scratch-resistant than both mineral and plexiglass. Because the sapphire glass is so hard (3x more than mineral glass and 20x more than acrylic, and second only to diamond) it is also more brittle and can shatter easily. Some covers are made up of combined sapphire and mineral glass.
Therefore sapphire crystals (and the thicker the better) are more preferred over the plexiglass and mineral glass.
Watch case material
There are several types of metals used for watch cases: stainless steel, 18ct gold, platinum, and titanium.
Stainless steel is the most common alloy used for dive watch cases and bracelets. Because of its durability and anti-corrosiveness, it is the ideal metal in dive watches. Grades of 316L and 904L are the types commonly used.
Gold is the second most common alloy in watches and can be either a gold-plated or PVD gold coated gold dive watch. There are differences between gold plating and a PVD coating. Gold plating is a process where a thin layer of gold (measured in microns) is electro-chemically coated over another metal (usually stainless steel in watches). However, people tend to prefer the PVD (physical vapor deposition) where the gold is vaporized in a vacuum chamber under high temperature and deposited on the watch. It is a more durable form of coating, is anti-corrosive to saltwater and doesn’t sweat like gold-plating. Because it is a more durable it is used in medium to high-end dive watches.
Platinum is also used but is very exclusive and expensive. The best dive watches that are encased in platinum impart wealth and prestige and command extremely high prices in the thousands of dollars.