YOU SAID:
the blue fish once lived alone in the sea of oceans
INTO JAPANESE
青い魚はかつて海の海に一人で住んでいました
BACK INTO ENGLISH
The blue fish used to live alone in the sea.
INTO JAPANESE
青い魚は海で一人で暮らしていました。
BACK INTO ENGLISH
The blue fish lived alone in the sea.
INTO JAPANESE
青い魚は海に一人で住んでいました。
BACK INTO ENGLISH
The blue fish lived alone in the sea.
That didn't even make that much sense in English.