It really doesn't look all that low poly now. However that's because you subdivided it.
You really have alot of wasted polys (they don't add to the shape at all).
I'd back up a step. Go back to the low poly before the subdivide (all that does IS add polys in between the polys you already have).
Then I'd clean up the poly distribution to get rid of weird lighting issues that might arise. Namely in the blue part in a few spots.1: By the back where it gets taller, there are alot of triangles and the rest of your mesh is stil quads.
The handrail areas have WAY too many polys and are smaller than the ones on the hull (weird lighting, wasted)/
In the front of the blue area there are some weird poly shapes. Can't tell what's going on there.
Anyway, once the low poly is clean and uniform, then you can use mesh smooth to subdivide AND make everything rounder. Don't confuse that with the smooth modifier (that only effects how smooth it renders, no poly change).
(I'm talking 3ds Max)
However to me it looks like your low poly is probably 3 sections tall for the main part of the boat (plus some for the tall back part).
Mesh smooth is really not the way to go, you're better off just modelling with more polys.
For Best results:
Turn your low poly into an editble poly. (not edit mesh)
Drag and select all vertical edges in the middle section of boat. Hit the connect dialog roll out and choose 1 or 2.
This will and a new loop of polys in there, you can then pull those edges out a bit to round out the basic shape and still keep it lower poly.