"I couldn't stay in the sea long because I got stung by a jellyfish."
"I couldn't stay in the sea long because I got stung by a jellyfish."
"I couldn't stay in the sea long." 「海に長くいられなかった」
"because ~" 「〜ので」
"I got stung by a Jellyfish" 「クラゲに刺さされて」
[刺されて](https://eikaiwa.dmm.com/uknow/questions/7052/)についてもっと詳しく知りたい方はクリックしてください。
I got stung by a jellyfish and it really stung. I couldn't stay in the water very long after that.
この場合、次のような言い方ができますよ。
ーI got stung by a jellyfish and it really stung. I couldn't stay in the water very long after that.
「くらげに刺されてすごくチクチク痛いので、あまり長く水の中にいられなかった」
to get stung by a jellyfish で「クラゲに刺される」
to sting で「ヒリヒリ痛む」
ご参考まで!