Unfortunately, that we can not guarantee. At the current layout there are tables for 2-4-8 on the boat. Of course, for a six-person group the table is only for the group. However, when there are fewer people, you may have to share the table with others. On the other hand the room on the boat is more limited than in a restaurant. The experience, however, will definitely be amazing.
However feel free yourself to make a booking for a private boat tour - meaning a whole boat for you and for who you want to see on board