because I like the design for the ship. I like German WW2 super large battleships. I have a game for PS2 called naval ops warship gunner 2 and I just let my imagination go wild with the ship designs. I am going to customize the ship I am talking about here to the point so it can have both ww2 tech and modern day tech. for example the ship is not using propeller shafts because it cannot provide enough power to make it move so I will use 3 of my prototype super turbine water rocket engines. Later on I will post a picture of what it looks like, because now I haven't designed it on my laptop yet just on paper, with this engine the water pressure output is 900psi because what is making the water going through the engine accelerate.
Then you can model it. You don't need to build it in real life. It would bankrupt most local-scale economies instantly.
the top speed the ship goes to is unknown because I have to build it in real life.
No, you don't. You can use some rudimentary freeware engineering programs (like Springsharp - Google it) to tell you that it will be slow.