The power transferred from the water jug to Gaelion, becoming an embodiment of magic. If I'm not mistaken, this magic created a magic water membrane. It can be used to weaken the effects of fire attribute magics. It's probably useful when you want to go into fire. For practical uses, it seems like it could be used in place of air-conditioning when it's hot.
"I'm guessing there's no magic book or anything." (Naofumi)
"I suppose. This magic is completely different from the process of how you and others materialize magic from your own power. You use power borrowed from other mediums, after all." (Gaelion)
"Before, you didn't embody power from yourself?" (Naofumi)