I know there are many of these cables that have been around for years, but I am curious how are they physically secured? Especially where they transit from ocean to land? Is there some long underground/sea tunnel of conduit that the cable is routed through to the basement of some building? Or if you are walking along the beach somewhere is there just some cable running out of the ocean along the beach to some building near the shore?

I also wonder what kind of permissions and licenses you need to seek to run a cable across the ocean floor?