|>>|| No. 13396
Navigation at sea is a lot harder than it looks. Vessels collide, run aground and experience near-misses on a daily basis. A large oil tanker takes several miles to do a 180 degree turn; a minor confusion or misunderstanding can very easily turn into a disaster. By the time you've realised that you've misjudged your speed or distance, it may well be too late. The COLREGs are very clear on paper, but they're far less clear when you're navigating difficult waters in poor conditions and the other vessel isn't responding to hails or is captained by someone who barely speaks English.
Back in 2010, HMS Astute ran aground off the coast of Skye. After becoming beached, one of the tugs sent to rescue it collided with the stricken submarine. Like most accidents, it was a series of minor lapses of judgement that turned into an almighty cock-up. The officer of the watch was inexperienced, he hadn't been properly briefed, he was rushing because the vessel was late for a rendezvous, the bridge crew were inadequately trained and unfamiliar with their navigation equipment. The stars aligned in just the wrong way and a billion quid's worth of submarine crashed into the bottom of the sea.