How deep can modern submersibles go; such as Alvin and Sea Cliff II?

DSV-4 can dive 5,000 feet (1,524 meters) deeper than the famed Alvin; however, the Super Alvin-class replacement for DSV-2 is designed to dive to 22,000 feet (6,705 meters).A nuclear submarine can dive to a depth of about 300m. This one is larger than the research vessel Atlantis and has a crew of 134. The average depth of the Caribbean Sea is 2,200 meters, or about 1.3 miles. The average depth of the world's oceans is 3,790 meters, or 12,400 feet, or 2 1⁄3 miles.