Watering it down as a punishment doesn't seem to make a lot of sense. I have read that the rum ration was mixed with fruit juice both to extend the drink and l

Watering it down as a punishment doesn't seem to make a lot of sense. I have read that the rum ration was mixed with fruit juice both to extend the drink and likely to attempt to combat scurvy. This is where 'grog' comes from, which is rum mixed with fruit juice.