Yep, that's a boat (water cooled) manifold. Not sure I would call it crazy though, a lot of thought went into it. "Wet" manifolds serve two purposes. First is to warm the incoming cooling water before it hits the cylinder head. Second is to reduce exhaust manifold temp. Typically inboard applications have the engine in a small space below deck. Hot exhaust plumbing and wood/fiberglass boat hulls don't mix.