Lagoon Gardens

In 1884, an exceptional book was published, written by a British expat, Frederic Eden: A Garden in Venice. 

It's a book provides most valuable insights into gardening (and living and cooking) in the Lagoon: Frederick Eden moved from England to Venice for health reasons in 1884 with his wife Caroline (the elder sister of Gertrude Jekyll, the famous English gardener). They bought a large garden on the Venetian island Giudecca and lovingly maintained and shaped it for almost two decades. As time passed by, they succeeded in turning this neglected piece of land into a flourishing paradise. 

A book that could serve as gardening course for tending gardens in the salty environment of the Lagoon: The book describes the experience the gardeners made, learning about the Lagoon habitat, and why some plants take well while others will never grown. 

Two websites describe the garden very vividly, Fictional Cities and an article by the Daily Mail.
Giardino Eden seen from above, by Google

This secret garden still exists, spreading on the Rio della Croce: Its last owner was the Austrian artist Friedensreich Hundertwasser, and the garden was renamed accordingly. After the death of its owner, the garden was closed to the public, and it remains to be seen whether one day it will be restored to its former beauty ...though based on the book Venezia insolita e segreta it is being tended to the bare minimum by occasional gardeners.