Collapse of Composite Submarine Pressure Hulls

Submarine pressure usually collapse if their external hydrostatic pressures are too large. If the strength: weight ratio of the submarines' materials of construction are high, submarines can usually dive to greater depths than if they are not. The hydrostatic pressure at the bottom of the Mariana Trench is about 1100 bars! This video shows some experiments, where model submarine pressure hulls were tested to destruction under external hydrostatic pressure.