http://sampit.geol.sc.edu/Doppler.html
"Moving observer: A man is standing on the beach, watching the tide.
The waves are washing into the shore and over his feet with a constant
frequency and wavelength. However, if he begins walking out into the
ocean, the waves will begin hitting him more frequently, leading him
to perceive that the wavelength of the waves has decreased. Again,
this phenomenon is due to the fact that the source and the observer
are not the in the same frame of reference. Although the wavelength
appears to have decreased to the man, the wavelength would appear
constant to a jellyfish floating along with the tide."


Ahh yes.

If you could find such a "jellyfish" for light; an object that is
demonstrably at rest with the medium through which light travels, then you
would destroy SR.

You haven't actually got a jellyfish, have you?

Let us know if you find one.