Hermione appears to be choking. He pauses, watching as she ducks under the water then emerges sputtering. She... wasn't aware he'd be naked?

"I believe this is the normal apprach," he offers. Although he can see, of course, she chose not to. He considers this, then moves a little deeper into the water. "Since we wash before entering the hot springs, my understanding is it is also considered more hygienic then wearing any additional layers."