SEA ROUTES.. how to establish... geez i just found myself in situation where i couldn't trade luxuries with 3 other civs because I hadn't "established sea routes". Heck, I have harbours, I have caravels (by now I even have a destroyer). What do I have to do to establish sea routes? If my caravel goes anywhere near the shore of another civ, the civ gets crabby. Grateful for help.