In video of the incident, her fiancé and one of their children are seen holding on to a branch to avoid being swept away.
The family, which included the pregnant woman who is eight months along, her fiance, their 2 kids ages 8 and 4, their 60-year-old uncle and a dog were all rescued by volunteers from Wild Florida, an airboat tour company from the Orlando area.
Photos of Florence's destructive path:
"By the time we had gotten there, they were holding on for four hours — two hours of which they were holding on in the dark, complete darkness," Jordan Munns of Wild Florida told Inside Edition. "They had all said when they were on the boat they assumed they were going to die because they would no longer have the energy to hold on and get swept away.”
The volunteers say it took them about 35 minutes to get the family aboard the boat.
The tour company posted video of the rescue on Facebook, where it has been viewed more than 5,000 times.