Source : Webster's Revised Unabridged Dictionary (1913)

--Totten.

   {To cross the line}, to cross the equator, as a vessel at
      sea.

   {To give a person line}, to allow him more or less liberty
      until it is convenient to stop or check him, like a hooked
      fish that swims away with the line.

   {Water line} (Shipbuilding), the outline of a horizontal
      section of a vessel, as when floating in the water.

Water line \Wa"ter line`\
   1. (Shipbuilding) Any one of certain lines of a vessel,
      model, or plan, parallel with the surface of the water at
      various heights from the keel.

   Note: 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.

   2. (Naut.) 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.

   {Water-line model} (Shipbuilding), a model of a vessel formed
      of boards which are shaped according to the water lines as
      shown in the plans and laid upon each other to form a
      solid model.

Source : WordNet®

water line
     n 1: a line corresponding to the surface of the water when the
          vessel is afloat on an even keel; often painted on the
          hull of a ship [syn: {waterline}, {water level}]
     2: a line marking the level reached by a body of water [syn: {watermark}]