Submarines - military combat; Submersibles - scientific exploration.
Submarines - larger, high capacity; Submersibles - smaller, limited capacity.
Submarines - great depths; Submersibles - shallower depths.
Submarines - powerful engines, high speed; Submersibles - limited speed and range.
Submarines - large crew, long-duration missions; Submersibles - smaller crew, shorter missions.
Submarines - armed and defended; Submersibles - not armed or heavily defended.
Submarines - stealth features; Submersibles - bright colors, lights for visibility.
Submarines - expensive, government-owned; Submersibles - varied sizes, commercially available.