I think you might have missed the point...
I can set the sensor to be always in the water, but not effective if the helo is moving.
The only practical consequence of doing it this way is that there is no delay in the sonar becoming effective when the helo stops... and this I can compensate for by making the sensor less sensitive than the sensor for the human dipping sonar.
Give me some more credit than that sid...
I have been testing this, and it works beautifully.