Just tried this mod after having spent some time playing with OM.
Incredible. Love it !
The rule is the 100 fathoms rule
(1 fathom = 6 feet, it's a unit of depth used by combat scuba divers - the first water resistant watch was designed for the English Scuba Commandos, the Blancpain 50-fathoms, first ever to work under water on wrist)