Zuko allowed himself to grin at her efforts, amazed at how quickly she got the movement right once she figured out how to do it. She was a fast learner, which explained how she'd advanced her waterbending skills so quickly. Katara could barely bend when he'd first encountered her and had kicked his ass with it just months later at the North Pole. It was impressive, to say the least.
"Not if I have anything to do about it," tumbled out of his mouth in response to her question before he could stop himself. Crimsoning a bit, he looked elsewhere and cleared his throat. "I mean, it's, uh, a possibility. Waterbending can only get you so far. You might come across something that's immune to water--or even thrives on it. And with the way things have been going in this city lately..."
He trailed off and was silent for a bit. Almost hesitantly, he began to speak again. "What if Wolfram & Hart decide to take away the moon next? You'd be powerless and vulnerable without your bending. Like I'd be if I hadn't learned martial arts and swordsmanship alongside bending. You need to be prepared to defend yourself in any situation."