Someone explain this to me

I understand nothing about submarines. How the hell does this happen? Is it that crowded down there?

LONDON -- Nuclear-armed submarines from Britain and France collided in the Atlantic Ocean earlier this month, authorities acknowledged Monday -- touching off new concerns about the safety of the world's deep sea missile fleets.

The HMS Vanguard, the oldest of Britain's current nuclear-armed submarine fleet, and the French Le Triomphant submarine, which was also carrying nuclear missiles, both suffered minor damage in the collision. No crew members were reported injured.

Update: I just realized England-France is coming up in the Six Nations. The nickname of that game? Le Crunch. Ha! (I am probably the only person who thinks this amusing.)