Final answer:
Finn remembered that the feeling of relief and comfort associated with drowning made swimming easier for him.
Step-by-step explanation:
Finn remembered that swimming became easier when he let go of his fear and embraced the feeling of relief and comfort that came with it. In the text, it is mentioned that Finn reflected on the idea that drowning could be like a comfortable arrangement and a cessation of hostilities. This realization helped him overcome his fear and made swimming easier for him.