How do modern submarines withstand deep-ocean pressure?

The answer

Submarines resist ocean pressure through hull design and material science. Most military submarines use a double-hull structure with a pressure-resistant inner hull made of high-strength steel or titanium alloy, typically 2 to 6 centimeters thick, shaped as a cylinder for optimal pressure distribution. The Russian Komsomolets submarine, made with a titanium hull, reached a record military depth of over 1,000 meters. Research submersibles go far deeper: the Limiting Factor, designed by Triton Submarines, uses a 90-millimeter-thick titanium sphere rated to full ocean depth of 11,000 meters. The spherical shape is critical because it distributes pressure evenly across the entire surface, unlike cylindrical shapes which concentrate stress.