For Catamarans, it is common to find a bare boat that has 3 or 4 cabins from 37 to 47 feet long. There are a smaller amount catamarans that are 50 feet and have 4 normal cabins and then one with bunk beds or is accessible from the topside. I do not include the “coffins” aka crew quarters in this list, because it is not realistic to use these for much more than storage. If your group is larger than 5 cabins worth (10 ish – you may have some kids in there), likely you have moved into a situation where you need a captain. There are catamarans in the 60-80 foot range that can accommodate large groups. Our group is considering a 600 Catlante for our next adventure if we can get a reasonable price. Another option is two or three sailboats, but mooring/anchoring together and lashing the boats together seems less than ideal.