With a catamaran you can sail from the port of Hamburg to reach lower Saxony, go across the Elbe, and head towards the fruit plantations of the so called "Old Land" (Altes Land). It's the largest area used for growing fruit on the continent.
You will love this excursion, the freshly picked fruit and thatched farmhouses, the vast landscape and the picturesque towns of "Buxtehude" and "Stade". It takes about an hour to get here from Hamburg, 50 km by road). It is truly unique.