Defining the waterplane
-----------------------

In order to do the final analysis you must first
define the level of the waterline.

You do this by creating a "waterplane". Enter the vertical
level of the waterplane along the Y-axis of the basic coordinate
system. This may be a positive or negative number depending on
where your coordinate system is located.

The waterplane is displayed as a rectangle with the text
"WL" in one of its corners.