[ What makes him decide to stop her is not the fact that she's about to rip into his neck (okay -- maybe a little bit of that), it's mostly the thought of her getting upset over this. He doesn't want her to have any regrets that she'd fed on him because it's fine. It's okay. It happens.
Better to lose control now with him than with anyone else in this place. She needs to understand that she's a predator. Not a puppy. And now that she's gone a little overboard, she can learn to take it down a notch. He intends to help her with that. ]
Elena... [ He pushes her gently at first, not wanting to startle her, not wanting her to freak out, but she's strong and she's still hungry (that's not even a little surprising as he could feed on five easily, so what's one?). Left with no choice, he uses the last ounce of his strength to turn their positions around again before pressing his forearm against her chest, keeping her in place as he presses his hand to his neck, covering that still gaping wound. What should be healing isn't because -- there's the whole slow healing issue in this underwater dome and the fact he's lost a lot of blood. It's a miracle he's still standing, but he needs to make sure that she's okay. He needs to let her know that she hasn't done anything wrong. He needs to maybe... sit down first. ]