The standard requires the ability to pass a number of tests including of course a battery of water
link resistance tests and diver's watches must also possess certain design features including the
link ability to be read in total
link darkness at a distance of 25 centimeters and as well they must possess a unidirectional timing bezel this has been an essential feature of true diver's watches going all the way back to the early 1950s when the Rolex Submariner and Blancpain Fifty Fathoms debuted.