A close encounter with a great white shark nearly ended the honeymoon, literally, for one man in South Africa.

The man, identified only as "Roger" in a video posted on YouTube, was diving in the waters off Gansbaai, South Africa, last Thursday when a great white shark made a grab for him and a fellow diver inside a cage.

Instead of going after the bait outside of the cage, the shark dove for his head, with his jaws wide open, inside.

"For the first few seconds, you can't help but think the worst has happened," said Bryan Plummer, the fellow shark diver who captured the terrifying scene on camera.

The honeymooner, who had just said "I do" the day before the dive, according to Plummer, managed to swim down just below the shark's open mouth and avoid injury.

"His instinct was to just go down and avoid where the shark had access to," said Plummer. "[It was] very quick thinking on his part."

The terrifying moments before it was clear that both divers had survived were captured on YouTube by Plummer who described it as an "out of control situation."

"Apologies for any profanity in the video," Plummer writes in his description of the clip.

Experts say the shark was acting on its natural instincts.

"When they get the scent of blood or scent of fish in the water they can go into quite a frantic feeding-type frenzy," said Ken Ramirez, executive vice president of Chicago's Shedd Aquarium. "They just sort of devour and hit everything in their path."