I live in a float cabin on Powell Lake, BC. We have a water lease, but no land. I still wanted to garden, so my friend John built me a float garden. It has four raised beds on a cedar log float. The bottoms of the beds are covered with porous heavy cloth (mill felt) so that water will run through and not waterlog the soil. I grow asparagus, strawberries, carrots, beets, lettuce, kale, chard, onions, flowers and herbs. I have a solar powered bilge pump garden hose for easy watering.  I also grow tomatoes, potatoes, garlic, peas, and beans in large pots on the float cabin deck. It's not enough to be self-sustaining, but enough to add to our meals, especially in summer. - Margy