When Sebastian had pushed her over to Derek. Emily had expected them to share a brief goodbye. Then for them to take one last shot at Sebastian. Maybe throwing themselves at him in unison. That way they would die with one of them, at least having landed a punch or a kick.
But then Derek had told her his plan of jumping, and she'd said yes without thinking too hard on it. But her agreement with the crazy plan had not been for her sake. Instead, she had done it for Derek's.
She had known that no matter what happened, Derek would not leave her behind. If she charged at Sebastian like she had wanted to do. Then Derek would have followed, dying by his uncle's hand. And if she had headed to the car when Sebastian had been ordering them to get into it.
Then Derek would have done the same as well, drowning alongside her.
Emily could not swim, but Derek practically lived in the water.