A family of three pulled out to sea this week in Massachusetts by a strong riptide captured the frightening incident on camera.
Erynn Johns, 16, was filming her holiday swim in Nantucket on a Go-Pro camera attached to a selfie stick when she and her father, Derrick, were dragged out to sea by the undercurrent.
She kept filming as the pair became increasingly desperate and Mr Johns grabbed hold of the camera to help get his daughter back to shore.
Lifeguards and onlookers rushed to help, and both father and daughter were eventually pulled back to shore safely.
Rescuers told Mr Johns he had only another 20 seconds before he went under, his oxygen levels were so low from the struggle.
"Just pure exhaustion seeing your daughter in the waves and your wife go down, and not wanting to let them go down," he told CBS.