A lot of my cities seem to be be near the coast..it varies from game to game, of course.  I keep looking at all this unproductive tile space that extends into the sea giving me nothing.  How about some sea tile improvements? following some sort of appropriate research.  I mean, there could be a sea tile for food or magical godzillas or some kind of sea horse or mer creature.  Or some sort of magical perk.

I just seems to me that it would be great if some of those water tiles could do something.