A dive watch is a timepiece made to be worn while diving underwater. At the very least, it must resist water to a pressure above 1.1 MPa, or 11 atmospheres. The international standard ISO 6425 sets out the tests and features a watch needs to qualify for diving with breathing equipment.
What features does a dive watch need?
Keeping water out is only part of the job. A diver must also be able to read the watch. The dial, the hour markers and the bezel must stay readable underwater and in dim light, where there may be little to see by. Some watches built for saturation diving add a helium escape valve. It stops gas pressure that builds up inside the case from forcing the crystal off.
Not to be confused with
A dive watch is not the same as an ordinary water-resistant watch. The Water Resistant mark rests on a separate standard, ISO 2281. None of the tests in ISO 2281 is enough to qualify a watch for scuba diving. So the Water Resistant mark alone does not show that a watch is fit for diving. For that, a watch must meet ISO 6425.
Where it comes from
Omega’s rectangular Marine of 1932 had a patented double case that slid apart and could be removed. It is credited as the first diving watch made industrially for sale. The Blancpain Fifty Fathoms appeared in 1953. It was developed by Jean-Jacques Fiechter, a keen diver who ran Blancpain from 1950 to 1980, together with French combat divers. One of his requirements was a bezel that turns, so the diver can time a dive with it. Today, most divers use personal dive computers instead of dive watches.
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