The correct answer is option 'D', which states that Douglas experienced mixed feelings of confidence and fear when he was thrown into the pool. Let's explore the series of emotions and fears that Douglas went through in detail:

1. Fear:
When Douglas was thrown into the pool, his initial reaction was fear. This is a natural response when faced with a situation that is unfamiliar or potentially dangerous. He may have been afraid of drowning or not being able to swim properly.

2. Lack of Confidence:
Before being thrown into the pool, Douglas had expressed his lack of confidence in his swimming abilities. He believed that he couldn't swim and was fearful of the water. This lack of confidence would have contributed to his initial fear and anxiety.

3. Overconfidence:
However, once Douglas was in the water, he realized that he could actually float and move his limbs to stay afloat. This newfound ability gave him a sense of overconfidence. He started to believe that he could swim and became less fearful.

4. Mixed Feelings:
As Douglas continued to swim and gain more confidence, he experienced mixed feelings of confidence and fear. On one hand, he was proud of himself for overcoming his initial fear and learning to swim. On the other hand, he still had moments of doubt and fear, especially when faced with new challenges or deeper sections of the pool.

5. Gradual Improvement:
Throughout his swimming journey, Douglas gradually improved his skills and gained more confidence. This improvement was accompanied by a decrease in fear and an increase in self-assurance.

Overall, the series of emotions and fears that Douglas experienced when thrown into the pool can be summarized as a transition from fear and lack of confidence to a mixture of confidence and fear, ultimately leading to increased confidence and decreased fear as he continued to swim and improve his skills.