The flight took off from Hawaii in stormy weather back in December.
Flight tracking data shows a United Airlines 777 suddenly plummeted for 21 seconds and came within 800 feet of the water.
The aircraft was able to recover and regain altitude before continuing its flight to San Francisco.
Nancy and Mitch Maler from Fresno say they feared for their lives on the flight.
RELATED: United flight nosedives after takeoff, comes within 800 feet of Pacific Ocean, data shows
"It was like the Tower of Terror at Disneyland. I just felt like my stomach was in my throat. People were screaming on the airplane," recalled Mitch.
United Airlines says there were no injuries.
The plunge occurred a little over a minute after takeoff, the data showed.
"I said a prayer. I just thought this was it. I thought we're gonna die," Mitch said.
Neither the airline or the Federal Aviation Administration have said what caused the incident.
The National Transportation Safety Board announced on Tuesday that it is investigating.
A preliminary report is expected in 2-3 weeks.