The Rolex Sea-Dweller is a legendary dive watch known for its ability to withstand depths of up to four thousand feet, four times more than the Rolex Submariner. The Sea-Dweller Deepsea can withstand depths of up to twelve thousand eight hundred feet and has features a new closing mechanism called the Glidelock clasp which allows the size to be easily changed so the watch can be worn over a dive suit. The Sea-Dweller Deepsea is much thicker than the regular Sea-Dweller and features an improved version of the helium escapement valve used to allow excess helium buildup to escape during decompression. The watch uses the Rolex calibre 3135 automatic movement which is both precise and robust making it perfect for the deep sea conditions.