In addition to the rod and reel assembly is the fishing line which goes down to the clip (near the downrigger ball) and then on to the lure. This line is usually made out of monofilament line which is elastic- another spring like component.
Remember: The line is not affected by drag, however the lure is. As stated previously, in reality, everything beneath the surface is subject to drag.
Because the slack is
taken out of the line, the line itself is in tension. Due to the
properties of monofilament, the line also stretches substantially-
again subject to modeling by a spring equation.
In the fishing line
component of our system, the tension in the line above the clip is not
the same as the tension after the clip. Why? Because above the clip,
the reel has cranked down on the line. But after the clip, the tension
in the line is equal to the drag force acting on the lure in the
opposite direction. To break down the forces acting on the lure would
be the same as for the lead weight, so an extensive examination will be
avoided. The important point is that there is tension and potential
energy stored in the fishing line at equilibrium.