Two random thoughts:

1. I'm always amazed that anchors can seemingly hit a cable at the bottom of the ocean floor. Given how hard it usually is for us to find anything on the ocean floor with any precision, we seem to be able to drop anchors and cut cables with surprising accuracy.

2. Do the cables have slack in them to account for continental drift? I don't know how much we drift, but I'd imagine over time the cables would need some slack in them to make up for it.