T&T: Anchoring vs Existing Moorning

[Rudy and Jill]

Here is an anchoring situation which I am curious about.

Someone sinks a mooring, seldom uses it, except, let's say, they plan to use it only for a hurricane. 

If there is no boat attached to the mooring when you show up, is it legal to anchor so close to the mooring that your boat would interfere with the other boat, if that boat arrives after you did and wants to use the mooring Must you move, or do they have to go somewhere else?

What if there is only a small boat attached to the mooring, but due to its size, your boat is not interfering. Then a larger boat shows up and wants to switch places with the smaller boat, but if they do so, they will interfere with your anchorage? Must they go somewhere else, or must you.

Hmmmm?

Rudy and Jill
Briney Bug, Panama City, Fl