We stayed on Derk's boat for two nights and absolutely loved it. The boat is easy to get to by bus from the main train station and right near all manner of shops and sights. It was very spacious and comfortable, and was almost more like an apartment than a boat. I was a little worried about the toilet/shower situation beforehand (from other boat experiences) but they worked great! Derk was also easy to get ahold of and flexible with our travel schedule. I would highly recommend this place!