Only small submarines can be built strong enough for the depth involved here. The Navy DSRVs are built for a depth of 5000 feet, since that is more than the crush depth of any Navy sub. If one were to sink in water deeper than that it would certainly crush and there would be no chance of rescue.
Certainly the US Navy has some other very deep water capable equipment, but it would be for missions that they want to keep secret like tapping undersea cables and salvaging enemy wrecks.
Certainly the US Navy has some other very deep water capable equipment, but it would be for missions that they want to keep secret like tapping undersea cables and salvaging enemy wrecks.