These floating gardens are in Amiens, France and you need a boat to reach them. They have been there for 2,000 years and used to yield enough vegetables to feed the whole area. Now they are farmed by weekenders, although a few hardy souls, including this man, still sell their vegetables to the public every Saturday. He grows flowers, herbs, potatoes, tomatoes and peas.
The drawbacks to water gardening: everything must be transported, soil erodes at the edges and must be built up and the soil drains rapidly and must be watered.