After his misadventure in the pool, Douglas wanted to get into the waters of the cascades but the old fear overpowered him. His legs would become paralysed and icy terror would grab his heart. He could not enjoy the sports games like canoeing, boating and swimming.

Introduction:
Douglas is a character in the short story "The Swimmer" written by John Cheever. In the story, Douglas is hesitant to get into the waters of Cascade due to the memories of terror he experienced in the pool.

Explanation:
The answer to the question is option D - "Memories full of terror in the pool." This option best reflects Douglas's hesitation to get into the waters of Cascade. Here is an explanation of why this option is the correct answer:

1. Memories of terror:
Throughout the story, it is revealed that Douglas had a traumatic experience in the pool. He recalls being pushed into the pool by a group of boys and feeling scared and helpless. This memory has left a deep impact on him, causing him to associate swimming pools with fear and terror.

2. Fear and apprehension:
Douglas's memories of the pool have instilled a sense of fear and apprehension in him. He is reluctant to confront his fears and would rather avoid swimming altogether. This fear prevents him from enjoying the waters of Cascade, as he is constantly reminded of the past trauma.

3. Psychological barrier:
The memories of terror act as a psychological barrier for Douglas. They create a mental block that prevents him from taking the plunge and immersing himself in the waters. Even though he tries to convince himself that he should swim, the deep-rooted fear holds him back.

4. Impact of past experiences:
The traumatic experience in the pool has had a lasting impact on Douglas's psyche. It has shaped his perception of swimming and pools in general. The memories of terror are so strong that they override any positive associations he may have had with swimming.

Conclusion:
Douglas's hesitation to get into the waters of Cascade is primarily due to the memories of terror he experienced in the pool. These memories have created a psychological barrier and instilled a fear that prevents him from enjoying swimming. This fear is the main factor stopping Douglas from immersing himself in the waters of Cascade.