I should have made clear what I meant by "sits lower in the water", and I'm responsible for the confusion. Because the boat is a three-dimensional object, and

I should have made clear what I meant by "sits lower in the water", and I'm responsible for the confusion. Because the boat is a three-dimensional object, and because the subsurface part contacts the water in three dimensions, if it is scaled up with all else the same, it should still have the same waterline, but (obviously) its keel is deeper in the water. > I still can't intuitively convince myself that the waterline would shift when the model scales. Your instincts are serving you well, and the answer is simple -- I wasn't sufficiently careful in how I described it, and I let an error creep into yesterday's conversation. In fact, a model whose dimensions are held constant but is scaled up, should show the same waterline at all scales. Again, I apologize for sounding so sure of myself when I wasn't.