Gondor's sea power / Middle Earth economics

[CAB]

I have wondered for a while now about the role of sea power in the ancient world. Obviously, boats from long past couldn't project power on land as modern ships do (via guns, missiles, etc.), so what made them so important?

A little while ago, I finally (I am one lazy bum )did some reading about the rise of sea power in the Mediterranean, and got my answer. Military ships existed, first and foremost, to protect or prey upon other ships. Their importance was tied, to a very large degree, to the importance of sea-going trade. Considering that some cities (I think Athens and Rome are good examples) became dependent on food delivered by ship to feed their populations, the potential power of navies becomes very apparent.

So, to my questions. Doesn't Gondor's, along with it's southern neighbors', possession of navies essentially prove that those neighbors, and likely Gondor itself, depended on sea-going trade? Since there are few other potential coastal trading partners, doesn't it suggest that Gondor itself probably engaged in significant trade with these other countries?