Did you ever see a water bag of canvas, or hessian?
The canvas water bag was not a skin but it could hold water, and even cool it. There was some loss, with water moving through the fabric. However, it was durable and effective.
Consider these words of Jesus: No one pours new wine into old wineskins. The wine would swell and burst the old skins.[b] Then the wine would be lost, and the skins would be ruined. New wine must be put into new wineskins. Both the skins and the wine will then be safe (Matthew 9:16-17 CEV).