Marc's boat was a unique experience that we will never forget. The boat is a little funky but with the right attitude you will appreciate of special it really is. The location is a huge plus, right in the heart of Paris, yet at night it was quite peaceful since the boat is a bit lower than street level you don't get too much street noise. The Bateaux Mouches, police boats, and giant barges cruise by most of the day, some causing a gentle wake that will rock you to sleep. If we weren't in Paris it would be very tempting just to sit on the deck and watch the world go by. We had a rental car and being able to have secure parking right next to the boat was quite nice.
Marc was super accommodating even before check in, I had a few questions about the exact location in order to coordinate a scooter tour we had arranged the following day. Marc was happy to call the rental company and made sure the drop off our scooters went well.
If you are adventurous, flexible, and don't get motion sickness I would definitely stay on Marc's boat.