The Water Level option allows you to add a "water level" symbol anywhere in the view. To add a Water Level symbol:
Select Water Level from the toolbar or the Add Tool sub-menu of the Tools menu.
Click the mouse at the point where you wish to add the symbol (or enter x,y coordinates in the prompt line), and the water level symbol will be added at that location.
After a Water Level symbol has been added, it can be moved, rotated, formatted, etc. See the Edit Tools Overview topic for details.
TIP: the Water Level symbol can be rotated to any position, graphically with the mouse through the right-click menu.