You can create interior items. A brief tutorial is below:

To add bulkheads, bunks, cockpit seats, even consoles and such, extrude a handy boundry edge (the shear is good) by .1 units, then extrude it again by 2 units.

Zoom in on the first extrusion and delete the two lines that join the larger panels. This gives you a new panel floating in mid air.

Shape the panel to what you want (if a flat panel…to the length and width you want)(if a box by
extruding the edges further to complete the shape).

Assign the shape (or panels of a complex shape) to a new layer(s). Move the shape to the position you want
it by highlighting all the lines, using Transform/Move then shape it to fit loosely.

Use the shaded mode on the perspective view, along with varying the waterline to find gaps between the inside of the hull and the edges of your shape and adjust to fit.

Move the perspective view around with the points enabled to see if any penetrate the hull exterior.

Correct any that land outside the hull and this should get you quite close.

When creating panels with the offsets for the parts, allow a bit of extra to trim to fit.

In the layers properties add density and thickness to get a CG of all the panels to help with weight calcs.

Luan is 38 lbs per cu ft which is 1 4×8 sheet of 3/8″ ply…Ocumme is 28 lbs per sheet. 3/8″ is .375 ft thickness… for any other type find the weight of a 3/8″ sheet of 4×8 and this is the weight of 1 cu ft.

If you place a plane under or penetrating the waterline you must make it an enclosed figure for the hydrostatics to work. always extrude surfaces UP if possible so you have a sealed surface under the waterline and always extrude all the edges when extruding perpendicularly to a plane.