I'm guessing maybe it just nullified or diminished the water-based attacks. Dunno. I'm still trying to figure out how water beats rock. I mean sure, high-pressured-fast water can cut through rock, I get it, but that indicates you need high-pressured-fast shooting water. Not just any old random water attack. I mean the golem could've just reached through the bubble and grabbed the water dragon and went to town on it, but somehow...reasons.