If you read my post, i gave links to the ports/oceans included, aswell as the ships. I have no idea what Gibraltar for Med Ops means. But yes, definitely, NY to Rotterdam would be possible. You would start off in NY, leave the port, switch environments, be in an ocean, and when your done in the ocean, you will once again respawn in Rotterdam. To do this, you just need to use the included mission editor. I can explain in more detail, how to create a new mission, but im sure you will figure it out yourself.
Each vessel in the game, can be used in ANY environment in the game, there are no limits in the Free Roaming mode, they can be used wherever, whenever. Trust me, this game is worth the money!
Regards,
Jonah