the force acts outwards, but in an implosion, the force acts inwards. When a submersible is deep in the ocean it experiences the force on its surface due to water pressure. When this force becomes larger than the force hull can withstand, the vessel implodes violently. ...
Submarines were equipped with nuclear missiles as well, making it even easier to launch a devastating attack [sources: Locker, Dillin]. Other nations — the United Kingdom, France, China and Israel — all had nuclear weapons by the late '60s [source: Icanw.org]. The nuclear bomb loomed ...