Your geometry was too complex to simplify. So instead of doing some operation on your geometry, I managed to get a similar A-class catamaran model from GrabCAD provided by the user Kim Gremillet-Nguyen. The geometry was a .step file which was good. I simplify the geometry as much as possible and tried to mesh it following the same meshing technique done in the project here. The project with mesh and geometry you can find here.
I have created 2 meshes; Full and a half mesh. Since the model is symmetric, you can proceed initially with half mesh following the exact simulation setup as in the project above. Please mind the orientation of the geometry while setting up the case.
I hope this helps. If you have any question/s, feel free to ask.
P.S: Once you are done with the analysis, please make sure to add the name of the GrabCAD guy in the comment section of your project.