Query on explanation for electromagnetic field - Feynman lectures on physics

[physicsYum]

In 2-5, an analogy is given for electromagnetic field: two corks in water, and the effect of jiggling one cork on the other (probably the up and down motion).

Now, that sounded more like water is a medium propagating the energy. But the electromagnetic waves require no medium for propagation, right?

I know, this is an analogy from the introductory chapters. But am I interpreting this wrong?

 

[TheShrike]

I just started reading the Feynman lectures myself. No, EM radiation requires no medium. What I think Feynman is trying to get across here is that there is a time delay in the reaction of one cork to the motion of the other. This demonstrates that the speed of light (or equivalently, of propagation of changes in an E or B field) is finite.