In the future farming sea cities will exist

Wendy B. Murphy : writer
Floating atop the surf, a farming city populated by humans and tended to by robots will be built in the 2000′s. Robots will tend crops that will grow on floating platforms around a sea city of the future. Water from the ocean will evaporate, rise to the base of the platforms (leaving the salt behind), and feed the crops.

Murphy, Wendy B. 1984. The future world of agriculture. [New York]: Grolier.