Step 1: Problem.
Douglas had a fear of water due to a near-drowning experience in childhood.
Step 2: Role of instructor.
The instructor tied a belt around Douglas, which was attached to a rope and pulley. He guided him back and forth across the pool.
Step 3: Step-by-step teaching.
He taught Douglas how to exhale underwater, inhale at the surface, and eventually use coordinated strokes.
Step 4: Conclusion.
Gradually, the instructor built his confidence and helped him overcome the fear of water.
Final Answer: \[ \boxed{\text{The instructor trained Douglas step by step using a belt, rope, and pulley.}} \]