I just learned today that this stuff is rare.
I, to this day, thought that everyone could manually control their soft palate, pop their ears without using their lungs, and manually control their tensor tympani (the muscle that makes the rumble). I AM SHOCKED. I mean, I got no singing or diving training but apperantly people spend months to learn to control these things. Although I am a casual swimmer/diver. That explains why people look at me weird when I say "just lock your nose" before diving.