As we have learned from the many criminal cases here on WS eyewitness accounts are usually the most unreliable so I am not at all convinced that he took off around the pool and then came back, jumped up and grabbed her by the arm or waist and pulled her in. It just doesn't make sense after seeing the video below.
This is a much better video of what happened taken just seconds before the attack, from a different angle than the one we saw where she was swaying and bobbing back and forth with him. This appears to have been taken from the other side of the pool, facing Dawn and the back of Tilly. You can clearly see that she was laying down on the shelf rubbing him. He does not appear to be on the shelf at all but fully in the water. To me this makes it a bit clearer as to how her pony tail could have drifted into the water which he then grabbed pulling her in. I think he did the fast swimming around the pool AFTER he grabbed her...not before.
If you have trouble with it not playing by clicking on the arrow, then try clicking on the title just above it and it should play.
Video Before Killer Whale Attack - CBS News Video
If you look at this aerial video of SeaWorld it appears that she was in the large rock lined area that you see at the top of the screen at about 50 seconds into the video, not in the main stadium performance area. I checked the SeaWorld Orlando website and there are pictures posted by various people that have attended a "Dining with Shamu" event, which had just ended when the accident occurred, and it does appear to be held in this area.
http://news.yahoo.com/video/orlandowesh-16122564/aerial-view-of-shamu-stadium-at-seaworld-18330171
JMO and I am sure some will disagree but I am trying to look at it objectively to get a better understanding of how it happened.