Oris, long known for its professional-grade divers’ waterproof replica watches sale, achieved a watch-world milestone with its Oris Aquis Depth Gauge, introduced in 2013. It is the first divers’ watch that measures depth by allowing water to enter the timepiece — a feature that would normally be a serious divers’ watch no-no.

The patented system in the Aquis Depth Gauge uses the principle of the Boyle Mariotte law — named for the two scientists who discovered it — which states that if the volume of a gas is decreased, the pressure increases proportionally. How the system works is thus: the watch’s sapphire crystal, which is a full 50 percent thicker than an average one, has a channel milled into its side that runs counterclockwise to the dial and stops between 1 and 2 o’clock. A small hole at 12 o’clock leads to the channel, while a rubber gasket seals the join between crystal and case.

As the diver descends wearing the watch, the surrounding water pressure compresses the air inside the channel and allows water to seep in through the inlet at 12 o’clock. The edge of the channel changes from light gray to dark gray to differentiate between water and compressed air, indicating the depth, in meters, on a yellow scale printed on the inside of the crystal as the diver descends or ascends. Unlike other watches with depth gauges, there is no inertia in the system, which means no delay in displaying the actual, accurate depth indication.

Other features that make the Oris Aquis Depth Gauge suitable for professional diving are its stainless steel case, which is water-resistant to 500 meters and has an engraved meters-to-feet conversion scale on the screw-down caseback so international diving enthusiasts can make quick calculations; its unidirectional rotating bezel, with minute scales on a black ceramic inlay; and the easily adjustable folding clasp, which also has an “anchor” safety feature that prevents the watch from falling off the wrist.

The movement is the automatic Oris Caliber 733, based on an SW 200, which powers the central hours, minutes and seconds and the date display at 6 o’clock. The dial’s indices and hands are coated with white Super-LumiNova, which, Oris says, offers excellent underwater legibility. The case’s screw-down security crown is embedded into and protected by a stainless steel safety barrier.

The high quality replica watch, which comes on a rubber strap, is packaged in a special waterproof case with several useful accessories: a replacement metal bracelet, a set of tools to change the straps; a certificate with details on the Aquis Depth Gauge’s technology, and a specially configured cleaning device for the sapphire crystal.