One thing I always wanted was a sea terrain 'shallows' or 'sandbanks' - allowing only small surface ships, traders and transports to enter for an increased move cost, but giving a small gold and food bonus as well as a significant defensive boost - that could be reclaimed at significant expense by nearby cities in the later period. (The Dutch could do it cheaper, and keep polders too.)
Now we have flooding, this seems even more attractive. Not even the most dramatic marine transgressions in history have turned farmlands into sea of a depth suitable for submarines to dive. Shallows would either start on map adjacent to coasts, or as the result of lowlying terrain being flooded. This would mean losing a tile to the ocean would be a major setback, but not an irrecoverable one if the player is willing to make the necessary sacrifice in production.
I wouldn't mind a bit more chaos in underwater geography in general, including land-adjacent ocean tiles. And then there's the real fantastical stuff like currents and trade winds, which wouldn't actually be too hard to represent as the underlying principles are fairly simple.
Now we have flooding, this seems even more attractive. Not even the most dramatic marine transgressions in history have turned farmlands into sea of a depth suitable for submarines to dive. Shallows would either start on map adjacent to coasts, or as the result of lowlying terrain being flooded. This would mean losing a tile to the ocean would be a major setback, but not an irrecoverable one if the player is willing to make the necessary sacrifice in production.
I wouldn't mind a bit more chaos in underwater geography in general, including land-adjacent ocean tiles. And then there's the real fantastical stuff like currents and trade winds, which wouldn't actually be too hard to represent as the underlying principles are fairly simple.