when u have a solid part as a boat body you can simply calculate the displacement .
1.close the top of boat with a thin extrude .
there are some easy and useful methods for calculating displacement and water line by solid works .
of course there a lot of parameters in design but which one you will scarify for the other
there are some limitations in designing submersible devices according to the water pressure . positive buoyancy submersibles need more...
im working on designing a catamaran with two rotorks.
distance between two rotorks is 3 m and the top area will 9 x 15 m