Your best bet will be using an external program to create a mesh. Ship hulls are a unique shape, and so it’ll be quite difficult to achieve a perfect one in Roblox Studio. If you’re new to 3D modelling and programs such as Blender, you can check out a tutorial video to get a simple understanding.
For example, here are two short videos that go over the basics of creating the shape in Blender:
How to make Boat in Blender 2.8
TUTORIAL: BOAT IN BLENDER under 5 mins, How to create boat in Blender 2.83 LTS