Here a great number of disabled people used to lie - the blind the lame, the paralyzed and they waited for the moving of the waters
Less reliable Ms have the second clause about the moving of the waters and also verse 4 From time to time an angel of the Lord would come down and stir up the waters. The first one into the pool after each such disturbance would be cured of every disease he had.
How should we deal with the fact that there are discrepancies in the different Ms that we have our translations from? Carson suggests that this might have started life as a marginal note that explained the popular belief at the time. We know that the two Bethesda pools were fed from a larger Solomon's pool and the stirring of the waters might have a purely natural explanation.
It hardly matters to John's narrative whether the second half of verse 3 and verse 4 are in at all. So it's not worth making a fuss about. Trying to defend every last phrase in the KJV is likely to lead us into dark alleys. that's why most confessions of faith contain the words 'as originally given'.