For some reason when I settled a city with just 1 tile of ocean "coast" between the city and land, that city was COMPLETELY excluded from list of available trade routes - meaning that nor I, nor AI was able to establish a trade route to it, or from it (yes, it had 0/2 trade routes when I tried).
My glorious floating city of Atlantis... just that it would probably look better if I went Supremacy, or if buildings actually had some pontones and not just grow out of the water itself.... still, production and food problem solved by every single coastal city channeling resources to Atlantis, she probably grew to around 30+ by the time I finished exterminating the vermin on the map, but I fool forgot to look at it.. and even though ocean cities start with really low strength, by the time I was finishing she had about 190+ since I placed every wonder I built in there, I had to make sure she can take an army.. though floating cities are really hard to capture since you need to get a melee unit there (for Purity it's easy, just sending the basic Rover once it gets LEV, but I can't imagine trying to float there embarked with city and it's defensive satellite carving holes in you...)
That game took forever because Japanese (mod civ) covered entire pangea and even half the ocean with city on city.. I spent whole afternoon just cleaning up after him.. this screen is after I finally exterminated him (I had 5 cities total, the rest of the white dots are all his cities (or those he conquered before I declared war, and I even burned down half of them). Still, wonder where that hate came from. Probably because I can't stand seeing Harmony japanese.. Japan has to go SUPREMACY! maaan..
Why? For the glory of Satan of course
- just, yeah, as people can see, there's not much resources in the seas.. mostly you're super lucky to find 2 within the workable city radius