One would think water would be a tad more effective against the flames, but Jade was fortuitous that wasn't the only thing in his arsenal. However, the guy was charging him, and shielding might put him in a position to be hammered away at until it broke. So, Jade launched himself out of the way when he thought best, getting to a solid stance when he landed and summoning his spear to throw it at the boy's leg. He didn't want to kill him, just incapacitate. He had unconscious people to protect.