Mate there is a raft of stuff about territorial waters and the like to go have a look at on the internet.
There are all sorts of issues from mineral rights to fishing rights and the like.
And your only thinking about stuff you can see above the surface of the water apparently there are all sorts of fun and games going on under it as well with submarines getting a bit to close for comfort. Not un heard of for people hill walking to see a black fin sitting in a scottish sea loch with a load of lads putting plywood over a bit of it and painting it black.