In what can only be referred to as a freak accident, in 2009, a French and British nuclear submarine by chance collided into each while submerged. This happened while both vessels were on Atlantic ocean patrols, and luckily they were traveling so slow that it was not too damaging.
With 250 crew members, on-board a submerged collision can be catastrophic, and it seems the two submarines were both carrying nuclear warheads. Both submarines were able to make it back to their home port even though they were damaged. And both defense ministries from each nation announced that there was no need to worry, none of the nuclear material had been compromised.
But it does indeed beg the question, how good are these cloaking and stealth measures on nuclear submarines. Why can they not spot each other when they are just centimeters apart. Both British and French submarines routinely carry over 16 nuclear warheads on their submarines so you would think they would be taking extreme care when navigating the oceans.
According to NATO agreements, there should be arrangements to ensure NATO allies know about the whereabouts of their nuclear submarines. It seems on this occasion both countries were keeping the location a secret. Foundations that campaign for nuclear disarmed have claimed we are very lucky this freak accident did not turn into anything sinister such as radiation leaking into our oceans.
Military experts describe the collision as a one in a million chance, and they do not think it will ever occur again. Apparently, both submarines were traveling so slowly that they did not notice one another. In fact, the stealth abilities of these submarines are so high-tech that in the immediate aftermath, the French military was unaware they had hit a British submarine. They believed that they had collided with an object, which they thought was surely a drifting cargo container.
When you think these submarines are over 500 feet long it is pretty incredible they can move without being noticed at all.