Strangely this cool software allows me to scale the beautiful wave piecing catamaran ferry in length and width, but when height is scaled then suddenly the bow gets really long ; (
The reference point for scaling (and rotation) operations’ coordinates are (0,0,0).
I suggest you move your model in order to get the reference point at the center of the interface between the re-scaled part and the unchanged part, i.e. the part you wish to resize must have only positive vertical coordinates and the part you don’t want to change must have only negative vertical coordinates.
If you don’t want to change the length or the width, but just the higth, select the upper part and move it upward.