water line

noun5

1. •
   The outline of a horizontal section of a vessel, as when floating in the water.
2. •
   The line corresponding to the surface of the water touching any submerged object or body.
3. •
   The level at which water meets land along the shore of a body of water.

   • Little creeks ran into [the river] in the wet season, but now their dry mouths hung clear above water-line. — 1895
4. •
   Any one of several lines marked upon the outside of a vessel, corresponding with the surface of the water when she is afloat on an even keel. The lowest line indicates the vessel's proper submergence when not loaded, and is called the light water line; the highest, called the load water line, indicates her proper submergence when loaded.

   • The water line is to that Bend or place she should swim in when she is loaded. — 1627
5. •
   Any one of certain lines of a vessel, model, or plan, parallel with the surface of the water at various heights from the keel. In a half-breadth plan, the water lines are outward curves showing the horizontal form of the ship at their several heights; in a sheer plan, they are projected as straight horizontal lines.