Holy water is just plain water sprinkled with a little salt, which in ancient times symbolized incorruption and immortality. It has no magical properties, just a reminder of God's purifying grace. The water is only holy when the person who blessed it is very loving and compassionate, usually a priest or teacher of wisdom. The question is how can you tell if it is holy, just by looking at the water crystals. The water crystals will have sacred geometry like love or compassion.
This can be more explained by Dr. Masaru Emoto's work, which he explains emotion effect water molecules and then the water forms certain crystals depending on the person's emotion. For more information, check http://en.wikipedia.org/wiki/Masaru_Emoto