The ‘floating’ gardens of Mexico or Chinampas. Ancient islands were built by hand in lakes, fortified by planted willow trees, holding incredibly productive vegetable and flower gardens. The Chinampas were once capable of feeding hundreds of thousands of people. Some are still in use today, but are greatly reduced in area and productivity and threatened by pollution.
There’s a good article about them here: www.eatcology.com/chinampas-the-floating-gardens-of-mexico
I don’t really know about the climatic conditions required for these gardens, but wouldn’t it be amazing if we could try something like these in the UK?