The Wave node won't allow you to do this, see https://github.com/MrKepzie/Natron/issues/1698
The solution I have involves an SeExpr node with the following RGB script:
cpixel(1,frame,x,y+x2*sy*sin(2*3.1416*(x/sx - x3)/x1),2)
set the number of scalar params to 3.
x1 is the wavelenth (which must be nonzero)
x2 is the amplitude
x3 is the phase shift in pixels (which is missing from the Wave plugin, and which is the parameter you should animate)