Yeah, there are boats in that boat. They’re called gun yawls and they look like this. They’re basically large rowboats with a single cannon. The idea is that they’re maneuverable and hard to hit. Apparently they were very popular in Scandinavia, which is something you might have guessed from the picture, in which there’s a Danish flag that is almost as big as the entire vessel itself. Presumably, this is meant to be used as a sail in the event that everyone’s arms get tired.
I’m going to make three versions of this: one with cannons, one with ballistas and one with no armaments. I’ve got a ballista and five different cannons you can copy and paste onto the map or use as VTT tokens to arm it as you like.
There’s one other thing I wanted to point out. I drew a ship called the Ebonclad about two years ago. You can fit that ship into one of the floating fortress’ hulls. You can almost fit two into each hull. This thing’s pretty big.