I agree with Fisherking that this is an interesting concept.

But I think in all the disscussion about sailors and marines being used or not, the real point has been missed. This isn't about in-game amphibious landings but about the flexibility it can give you. There is no need to have the men rowing to the beach and starting a battle 9though it would be nice), opposed landings in this time period were something they would've avoided as far as possible.

I think the point is that sailors and marines mean you don't have to embark soldiers to raid far away places. As mentioned Morgan sacked Panama and raided far into Spanish territories (grenada, cuba, etc...) without dedicated soldiers. Their impact was huge though.

It has been stated that you can impact an enemy's economy by destroying provincial infrastructures, sailors and marines would be perfect for this in relatively undefended coastal areas. Fleets wouldn't just interdict the opposition's seaborne trade but also their land infrastructure (to a degree) without dedicating soldiers to the task.