I'd just like to say that there are two safety threats to submarines at sea, under water: one is from collision with another submarine, and the second is from interference from a surface ship conducting certain types of operations involving underwater equipment and so on.
The SUBOPAUTHs around the world act as the referee to keep all these components apart safely. The submarine movement advisory authority does so on an international scope because, of course, submarines often operate outside their own territorial waters, and it acts as a sort of an independent clearing house in that way. The system is very straightforward, actually, and it has worked very well for at least three or four decades that I know of. Everybody participates voluntarily but willingly.