Material Types & Print Size Questions

[CliffCox]

Not a printer & not very knowledgeable about 3D Printing: Have one experience; used entry-level online CAD to draw a part for a boat. Tried to duplicate a 4" diameter x 2" thick plastic cylindrical shape. I had one fabricated in a machine shop (has some intricacies like bores, hubs, screw holes, and a spiral groove around the circumference). The machined plastic was solid and therefore "heavy" and when I received the 3D printed one, it felt only 1/10th the weight. Put it under water and it soaked up enough to almost be as heavy as the solid one. It worked ok for the application but I didn't expect it was porous. So first question: Can a 3D print of a type of plastic, say PVC, be "solid" almost like a purchased piece of stock (or at least not porous enough for water to leak through the material)?

Next question: Is it possible to 3D print a simple, "plastic" of some sort, very small boat (visualize a small paddling boat but this one will have a small electric motor with footpedal steering installed after building - also see the pic attached) approx 10' long x 32" wide x 12" high and it be "strong" and waterproof (unlike my porous disc)? There would be plenty of details (structural parts/ribs/braces, storage boxes, double-walls for trapped air for flotation in case of getting swamped, wire and/or water conduits (tubes) printed into the side walls and/or floor (within the double-walls), "molded" mounting shapes for things like head lamp, gauges/switches, hardware mounting, etc. For this purpose (a fairly low cost item for the size), does this sound like a job way too expensive until some day in the future of 3D printing or feasible today? If feasible, any recommendations for printing services of this type/size? And what could be an off-the-cuff, out-the-air, top-of-the-head, ballparkish price (basically your best WAG) in the closest $100 (or $1000) range?

Many Thanks!!
Cliff

Boat.jpg