I suspect her family was drawn off shore when the water receded. They would not have had enough time to go out that far on their own and they seem to be heading toward shore. She probably went to meet them to help.
I was thinking that too, but they're so close to each other... if they had been swept away in the initial drawdown, and then when it went to sea floor level they started running on dry land, I don't think they would have been so close together. I think they went out there to explore, tragically.