I do seem to recall in Vanilla that you'd see navies from just above any nation swimming around in the 'Med, with one or two pirate fleet's yelling "argh, shiver me timbers" before being sunk with all promptness.
Now, probably in no small part to EB's fleet costs and upkeep, the A.I. doesn't even seem to find it prudent to build navies in the first place. I can honestly recall only two times when i've even seen another nation's naval forces outside of their starting ships.
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