It reminded me of teaching swimming (when in college). I specialized in kids who were deathly afraid of the water. There was a skinny little say 6-year old kid in Santa Cruz, and he'd probably had a water trauma, because he trembled when in the pool, wouldn't get his face near the water. His mom really wanted him to get over it.
I started him blowing bubbles, then harder and harder until his face was getting splashed. Then floating a short distance to pool's edge, face down. Progress. OK Eric, I said, I want you to ride on my back and we'll swim around. After I got him to relax a bit and loosen up on his choke hold on my neck, I started swimming. Then blowing bubbles as we swam. He got comfortable. OK Eric, I want you to take a breath and close your eyes and we'll go under water. We dove. Then under water with his eyes open, and voilà, Eric became a swimmer.