We were 17 and the boat is amazing for groups ! Fully equipped, you'll find everything you need to cook and eat, which is very comfortable. As the bedrooms are very small we were always in the main room, which creates links.
The boat has a great location, you can always take the tram to the city center (20 min) and the night buses.
We appreciated the reactivity of the crew when we had a problem with the heating the first night.
I strongly recommend this place for groups !