You will notice that the Navitimer you have makes no reference to being water resistant anywhere on the case. That is because even the genuine is not waterproof (3 Bars - resistant to splashing, 5 Bars is required for swimming). It is a pilots watch, not a divers watch. The reason is that because the sliderule is positioned inside the crystal, the whole bezel/crystal/sliderule assembly must spin. I would think that it would be impossible to get a moveable piece to be water tight.