Before boating season I was asking about taking the girls out on the boat and some wonderful YTers here offered these tips. Take those frozen ice packs wrapped in a towel for her to lay on, spray her with cool water, feed her watermelon and of course lots of water.
It's wonderful that there were such compassionate people there to help your little one. Thank goodness she was OK.
Don't be so hard on yourself. All's well that ends well and you had no idea this would happen.