WR 200M / 20 Bar Marking — What This Mark Means

A 200M rating indicates the watch was tested to 20 bar of static pressure and is suitable for swimming, surfing, and recreational scuba diving, which conventionally reaches a maximum of around 40 meters' depth. This is the entry standard for purpose-built dive watches, typically paired with a screw-down crown, a unidirectional timing bezel, and robust case construction.

Two distinct groups of watches carry the rating. ISO 6425 certified divers, marked "DIVER'S 200m," pass a battery of tests including overpressure testing at 125 percent of the rating, condensation checks, and legibility requirements, with every individual watch pressure-tested. General 200m sports watches, including most Casio G-Shocks with their standard 20 bar rating, meet the pressure figure without the full diver's certification.

The rating appears on the case back or dial as "WATER RESIST 200M," "WR200," "20 BAR," "DIVER'S 200M," or "WATER RESISTANT 660FT." On certified dive watches, the "DIVER'S 200m" wording usually appears on the dial itself, as on Seiko's classic divers.

G-Shocks typically print "20 BAR" on the dial or bezel rather than a meters figure.

"DIVER'S 200M" signals ISO 6425 compliance, while a plain "200M" or "20 BAR" does not. Above this level sit 300m watches such as the Rolex Submariner and Omega Seamaster Diver 300M, and professional pieces rated 600m, 1000m, or more, like Seiko's Tuna series, often adding helium escape valves for saturation diving.

Some vintage divers carry 150m or "660ft" markings from eras before 200m became the convention.

Not all 200m watches are certified dive watches: the ISO 6425 standard requires tests well beyond pressure resistance, so a 200m fashion-sports watch and a "DIVER'S 200m" Seiko are not equivalent. On the other hand, a helium escape valve is unnecessary for recreational diving; it matters only in saturation diving from dry habitats.

The rating also depends on maintenance. A 200m diver with decade-old gaskets may no longer meet its rating.

If you plan to dive, verify the watch carries ISO 6425 certification (the "DIVER'S" marking) rather than a bare 200m figure. Always screw the crown down fully before water contact, rinse with fresh water after saltwater use, and have the water resistance pressure-tested after any service that opens the case.

For desk-and-weekend use, a 200m watch simply offers a wide safety margin.