On tonight's episode (Feb 15) McDreamy found her in the water, and pulled her out. She was extremely hyperthermic and had thus quit breathing and flatlined. Because of the extremely low core body temp, she is less likely to suffer brain damage from oxygen deprivation. At the end of the episode, she saw the light, the color came back to her face and she sat up, in the room with her were Denny and Bomb Squad guy. She asked "am I dead" and Denny said yes. We are lead to believe that she is dead, but the staff have not given up on her yet, and previews for next week show Yang coming in and renewing the fight to save her . . .
Is she dead, maybe we will find out next week, but in the long run, I doubt it. Maybe for the next episode. This 3 part storyline ends with next week.