Marine Architecture is about as different from MCAD as Civil Engineering is from MCAD. In fact designing boats/ships is much more like civil engineering. I know several Marine Architects. All of them work in AutoCAD. There must be a market for the Pro/Engineer Hull module or PTC wouldn't have developed it. My guess is it was done in response to a very large account; something like Newport News or Mitsubishi Heavy Industries. Try finding a forum on Marine Architecture and posting there.
Sparkman and Stephens is the biggie here. Naval archecture invilves calculating prismatic coeffiecient, center of lateral plane center of bouyency etc. Not real hard to do, you can set up a spreadsheet program for most of it.
It is a very specialized field and as a designer you probably won't get involved in that end of it. Stress analysis is also very important so Mechanica is a plus.
Not sure what is in the shipbuilding module, you might want to check with PTC on that. I have designed small boats the manual way many years ago. AutoCAD is used because they had it first.
My guess is that you will be OK with the basic Pro/E package with Mechanica. If someone else is going to pay for it then get it, otherwise wait and see if you need what the module generates.
For the beginning I must give more details. I will not do construction job, but modeling - designing, redesigning and improving all of details of that ship. I will get sketches, and tips, ideas, to design something, and I will do job like that. For the beginning, I will make one part of passenger
I have modelled some equipment that is used on ships. To do the equipment correctly we had to build a Proe mock-up of parts of the ship's structure. We found that accuracy can be an issue when you're working with long & thin plates/beams. Change your accuracy to the lowest ratio but this has the downfall of longer regeneration times... lots of luck..