Lynn Fleming slipped in a small underwater depression when she was taking a stroll with her family in in the west coast of Florida, US.
She was left with a 3/4 inch graze below her knee which she described as “small cut”.
Mrs Fleming at first “dismissed” the cut and “didn’t think much about it”.
Her son Wade said he and his wife Traci managed to reduce the swelling.
But he said they became concerned when the cut continued to bleed.
Lynn went to the doctor a few days after her fall and was given a tetanus shot.
But the day after that she was found unconscious at her home and was rushed to hospital.
She died on Wednesday, two weeks after her fall – after suffering two strokes and sepsis.
Doctors had battled to save her leg which they said was infected with a flesh-eating bacteria called necrotizing fasciitis.
Her devastated family are warning about the dangers of the bacteria.
Speaking to Fox News, Wade said: “It seems like a ‘Lifetime’ movie really.
“I can’t even believe it, that it’s really even happening. It’s just all happening so fast.”
“You get the open wound while playing at the beach, watch it, take care of it,” he said.
His wife said her mother-in-law died after walking on “the place she loved”.
Traci said: “She couldn’t wait to get down here and retire,” she said.
She added that unfortunately the beach is a “place that took her life by freak accident”.