Rolex did a fairly incredibly P.R. stunt when they made the deepest diving mechanical watch ever for inclusion in the 51.4mm wide Deepsea Challenge.  You can check out what went into making the beast of a watch below as well as learn about the Deepsea Challenge.

On March 26, 2012 a vessel called the Deepsea Challenger emerged from the depths off the coast of Guam after spending several hours underwater. Looking like a lime-hued torpedo with two robotic arms, a single man crawled out of the hatch as cameras peered inside to see if man or meat jelly would step out of the green machine after it spent over six hours traveling to and then strolling on the sea floor in an environment with immeasurable pressure (well it is measurable). Box office king (and director) James Cameron casually came out of the tube. Who else? Wearing a Jacques Cousteau style head-warmer and trimmed-beard, the do-no-wrong film-maker and sci-fi visionary just finished going to the deepest bottom of the ocean. Almost seven miles underwater to the floor of the well-known Marianas Trench. James piloted the Deepsea Challenger 35,756 feet (10,898 meters) under water.