ocean improvements?

[apatheist]

I can only wonder what they were thinking. When I have a huge empire to govern, I don't want to spend my time laying nets in ocean.

I'm guessing you "build" a fishing ground. It's not something you have to do every turn. As such, it's no different from a land-based improvement.

 

[Atrebates]

Haven't the Japanese been planning an ocean city for a couple of decades now? I think they were planning to build one outside Tokyo...

Of course, plans don't always have to be realistic...

The Japanese use land reclamation fairly extensively, but that is dumping stuff in the sea till you have land. They had some bad experiences with earthquakes (eg Kobe), so now sink foundations to solid rock.
So it would be possible to have ocean cites in the manner of oil platforms but not justifiable, doesn't feel like civ