Need a wavy line? Try this:
Make a solid the width of your comp (i.e. 720 pixels wide) but only 10 or 20 pixels high.
Set the layer quality switch to high.
Then apply the Distort>Warp effect. Choose Flag for the Warp Style then keyframe Bend changing from -100 to 100 over the course of a second. Option click (Alt click) Bend's stopwatch and add the following expression:
This will make the wave loop so that it waves over and over again.
Finally, duplicate the effect (not the layer) five or six times to heighten the wave.