Wait, I think Great Britain and some other country were having a small boat war. They were blowing up each other's ships if the enemy's ship entered their water property. Britain, or the other country built a barrier between their ocean land thingy.

edit:
There was a ship that had over 1,000 people on it, and was blown up. The country that owned the boat was pissed off and sad. That's when the war started.
edit:
if you can get a picture of the world map and circle where Britain is, I can likely find the other country. I'm stupid and can't find it.