You don't have a theory ... you have guesses that are only supported by the number of other people repeating the same guesses.
It's easy to imagine wild guesses explain an unproven large number of alleged mystery crashes over water when you don't...
Sounds like you're the expert.
Now instead of suggesting things that might cause the issue you are concerned about, get the recorded flight data from some of these mystery crashes over water and find out what actually happened to cause the incidents.
So yeah ... you are just repeating the BS myths that you've heard and thus perpetuating them.
That has nothing to do with your drones-crash-over-water-mystery.
It's about obstacle avoidance might have troubles under certain circumstances.
For no reason?
How do you know this .. or is it just what you've heard people say?
This is like going down to the boat harbour and telling yacht owners that if they sail out to the horizon, they risk falling off the edge of the earth.
I think...
Except that makes no sense at all.
People have been flying over water since DJI started selling drones and no-one has ever had any problem with radio waves getting scrambled.