Deep-sea bathysphere physics involves extreme hydrostatic pressure calculations reaching 1,100+ atmospheres at Challenger Deep, requiring sophisticated material stress analysis using Von Mises calculations & safety factors of 2.0-4.0. Thermal dynamics create challenges through temperature gradients from surface conditions to constant 2-4°C deep ocean temperatures. Buoyancy systems utilize Archimedes principle with variable ballast & syntactic foam technology. Optical physics addresses light attenuation & viewport distortion affecting visibility. These complex physical phenomena require precise engineering solutions for human survival in Earth's most extreme environments.