In my opinion, traditional theories of what navies can do in diplomacy has been too simplistic: binary 'assailant' and 'victim' models with mechanistic approaches of A does something to B and B responds (eg Cable).
I expand on this in my book.
Instead, I think diplomacy is about representation and communication.
So, I define naval diplomacy as:
... a subset of general diplomacy and a means of communication by maritime actors, both state and non-state, in pursuit of their interests.
It's about sending a message.
More likely, however, it's about multiple messages to multiple audiences. This is where it gets a little more complicated.
We need to think about those directly involved, those nearby, those who are watching, and whoever pays the bills.