As she watched, the orca appeared to find her fascinating too, bobbing up and down in the sea and spraying water in her face.
Looking down at the orca beneath her, she saw them feeding on stingrays.
"The water was so clear. There were two orca and they were sharing the stingray. They had it in their mouths ...
"Then the little one was munching on the stingray and I could see bits falling off and floating in the water. The other orca was catching the bits and eating. It was such an exciting experience."
Mrs Hegan's husband and children got into a dinghy and joined her.
Alexandra had always wanted to see an orca and was thrilled when one swam right beside their vessel - blowing water into her face.
Mrs Hegan said: "I had always told her that she would have to see one in the wild as I would never take her to one that was in captivity.
"As she followed behind them in the dinghy, she was saying: 'Mum, my wish came true."'Vaimoana Tapaleao