YOU SAID:

I have a fish swimming in a large pond

INTO JAPANESE

私は大きな池で魚を泳いでいる

BACK INTO ENGLISH

I'm swimming fish in a big pond

INTO JAPANESE

私は大きな池で魚を泳ぐ

BACK INTO ENGLISH

I swim fish in a big pond

INTO JAPANESE

私は大きな池で魚を泳ぐ

BACK INTO ENGLISH

I swim fish in a big pond