[Mithalwen]

Yes, and I am no sailor but I am not sure that their ships - at least of the type that Aragorn captured would have been up to that sort of a journey. Going up the Anduin is one thing but the open sea? Crawling around the coastline would have taken forever and part of the coastline looks ratehr like the notorious Bay of Biscay. Althought I suppose the Black Numenoreans would have had the same seafaring knowledge as the true ones. They would also have had to get past Dol Amroth which seems to have had naval power.

So either the danger was in reaching the sea or Sauron had other resources. I am not sure the council anticipated the winged beasts but even so using them over water seems unlikely (though the thought of them landing on an elf ship as a Harrier does on the Ark Royal is quite funny).