Oris' new Aquis Depth Gauge might not be the first watch to let a diver track the depth of their underwater excursions, but it takes a unique approach to that functionality.
Instead of relying on electronics and sensors that can add bulk to a watch, the Aquis Depth Gauge features a thicker sapphire crystal with an air channel milled into the side that runs almost all the way around the dial. At the 12 o'clock position there's a small hole which lets water in when the diver gets deep enough for the surrounding pressure to compress the air in the channel. And using the numbers printed around the dial, they're able to read their depth by simply finding the spot where the water meets the air inside.
Known as a capillary depth gauge it's supposedly incredibly accurate, and there's absolutely no lag when taking a reading as it's perpetually being updated. However, it is lacking one important feature: the ability to remember what the diver's deepest depth was which is important to know when calculating a safe speed of ascent. So even if it does come in a badass waterproof briefcase full of tools and swappable straps, it's still kind of a bummer that Oris is asking $US3570 for a diving watch that might still require a separate piece of hardware.