Adrián Simancas and his father, Dell Simancas, were taken by surprise by the enormous whale, which suddenly emerged trapping the young man and his yellow kayak in its mouth for a few seconds before letting him go.
Dell, just a few meters away, captured the moment on video while encouraging his son to stay calm.
"Stay calm, hold onto the boat," he can be heard saying in the recording, which has become one of the most shocking and terrifying images in Chile in recent years.
"I thought I was dead," Adrián told the Associated Press. "I thought it had eaten me, swallowed me."
He described the "terror" of those few seconds and explained that his real fear only set in after resurfacing.