King James Version
And when they came to Marah, they could not drink of the waters of Marah, for they were bitter: therefore the name of it was called Marah.English Standard Version
When they came to Marah, they could not drink the water of Marah because it was bitter; therefore it was named Marah.New International Version
When they came to Marah, they could not drink its water because it was bitter. (That is why the place is called Marah. )