How deep can a sub go underwater?

A small submarine, the bathyscape Trieste, made it to 10,916 meters (35,813 feet) below sea level in the deepest point in the ocean, the Challenger Deep in the Marianas trench, a few hundred miles east of the Philippines. This part of the ocean is 11,034 m (36,200 ft) deep, so it seems that a submarine can make it as deep as it's theoretically possible to go. The water pressure at this depth is over 1000 atmospheres. Life does exist here, as well as a carpet of diatomaceous material that covers all the ocean floors of the world.

ANS 2 - A bathyscaphe is not a submarine. Most submarines can dive to about 1,000 feet, some of the latest to at least 14,500 feet, possibly more.