The Triton 36,000 is an amazing submarine. Previous generations of the Triton only went to 3,300 feet but the new model uses technology from Rayotek Scientific to make a passenger dome that reacts to increasing pressure from increasing depth by becoming stronger.
The passenger hull's material is called borosilicate glass (soda-lime) and its shape and material allow it to pack into itself and compress in such a way that that gives it more resilience as the surrounding water pressure jacks up. It should—in theory—allow the Triton to reach the deepest part of the sea, the Challenger Deep in the Mariana Trench, at a rate of 500 feet per minute, hitting approximately 7 miles down in 75 minutes.
The last time a vehicle did this, claims PhysOrg was 1960, and the Trieste, a bathysphere that carried two, was not in the least maneuverable, and carried a special edition Rolex called the Deep Sea Special (Mark III) to the bottom in a well publicized stunt that made rolex a legend. Functionally, the Rolex was also engineered with a super strong bubble face crystal.
The glass of the passenger compartment only reaches its pressure resistance of 16,000 psi by doing some crazy things. For example, it needs to use fiber optics to relay touch screen control signals through the glass of the 6-foot sphere. And the sphere itself is created to extremely high tolerances of geometric accuracy over 8 months by slowly and carefully heating and cooling the raw materials. These processes are the only thing that let the Triton 36,000—in theory—get as deep as it's rated to.
*The Triton is in a race to the bottom of the trench with at least Sir Richard Branson's Graham Hawkes designed Virgin Oceanic vehicle.