At school I had enjoyed reading Japanese literature in English translation, in particular Soseki's I am a Cat and Kokoro, and Akutagawa's The Nose and Kappa.
河童の川流れ。
The best swimmers are oftenest drowned.
「陸に上がった河童」とは環境が変わったために能力を発揮できずにいることのたとえです。
"A fish out of water" is a metaphor for being unable to use your talents due to a change of environment.