Keep in mind proper way to do CESA is ascending from deep. Which means there is a substantial change in pressure while doing it. Technically speaking aaahhhh is releasing extra pressure instead of true exhaling. You can't duplicate it on land or in a pool. In real life it's easier than it sounds.I just can't resist the urge to breath when I hit the 20-25second mark of making the AHHH sound when I practice on land or in the pool