Final answer:
The best supporting line from Sea Life that emphasizes the main lesson of the narrative - that everyone has unique strengths - is Option 4: I don't know exactly what kind of fish I am just yet, but hey, at least I'm swimming!
Step-by-step explanation:
The best supporting line from Sea Life that emphasizes the main lesson of the narrative - that everyone has unique strengths - is Option 4: I don't know exactly what kind of fish I am just yet, but hey, at least I'm swimming! This line highlights the idea that even though the narrator may not have discovered their unique strengths yet, they are still moving forward and making progress.