The lack of breathing didn't appear to be an issue for Beatrix. She was willing to push aside the discomfort for the taste of victory if she could get it. There was the satisfaction of watching him go under and yet, she found herself in his grasp again.
He might have felt at peace, but she was finally moving toward the surface for air and took a big gasp once her head was out of the water. Underwater combat was a lot trickier than being on land. Controlling one's breath had a whole different meaning. After the initial flailing, she tried to put a little distance between them to catch her breath and her bearings. If he had decided to pursue, she knew she was at a disadvantage due to his reach alone.