The Netherlands is so full of water that it's really a shame not to get on a boat once in a while. You can find plenty of tourist rides through the canals in central Amsterdam, or try out the paddle boats (if you dare). Or, if you're lucky, maybe you have a friend that has a boat with some spare room. There's nothing like motoring through the canals, waving at all the land-bound pedestrians.
Or maybe you're invited to a boat party. This was the craft that I once had the pleasure of sailing on for several hours. Complete with a knowledgeable captain, we celebrated an anniversary and a birthday and cruised through bodies of water much larger than the Prinsengracht. It is possible to rent one of these beauties - just get enough friends together so the price isn't terribly high, and away you go! It's a must-do in water-logged Nederland.
