I had a similar thing happen on a canoe trip. My brother (older former Navy officer who as it turns out had never been in a canoe before that day) and I were paddling a canoe with my 8 year old daughter and the cooler full of lunch in the middle when the canoe went sideways and started to get pulled under a rock. It was a slow roll and a flat rock so I was able to get out and lift the cooler out and then come back for my daughter. She still gives me grief about it.
Did you explain to her that the cooler had the beer?