YOU SAID:

I ate the beast of down up fire swam

INTO JAPANESE

獣を食べた火を泳いだ

BACK INTO ENGLISH

The fire ate the beast swam.

INTO JAPANESE

火獣の食べた泳いだ。

BACK INTO ENGLISH

Had the fire beast swam.

INTO JAPANESE

火獣は泳いでいた。

BACK INTO ENGLISH

Fire beast were swimming.

INTO JAPANESE

火獣が泳いでいた。

BACK INTO ENGLISH

Fire beast were swimming.