YOU SAID:

if a fish swims, he doesn't die

INTO JAPANESE

魚が泳いだら死なない

BACK INTO ENGLISH

If a fish swims, it won't die

INTO JAPANESE

魚が泳いでも死ぬことはありません

BACK INTO ENGLISH

Fish do not die when they swim

INTO JAPANESE

泳いでも魚は死なない

BACK INTO ENGLISH

Fish do not die even if they swim

INTO JAPANESE

泳いでも魚は死なない

BACK INTO ENGLISH

Fish do not die even if they swim