A humpback whale briefly swallowed a kayaker in southern Chile, before spitting him out unharmed, an amazing escape that was all captured on video.

Adrian Simancas was paddling off the Patagonian city of Punta Arenas on Saturday when the giant baleen surged out of the water swallowing him and his yellow kayak whole.

Five seconds later a stunned Simancas bobbed to the surface, as the whale’s dorsal again emerged above the surface of the frigid grey water.

“I thought he’d swallowed me!” Simancas exclaimed.

The entire remarkable episode was caught on camera and quickly went viral after being posted on social media by his father, Dell Simancas, who can be heard shouting “Relax! Relax!” to his understandably unrelaxed son.

“Grab it, grab it” the father adds, instructing his son to keep a hold of the kayak to stay afloat while the whale continued to swim behind him,

“Relax, relax, I’m coming,” the father says. “Let’s go to shore.”

The 24-year-old son told Chile’s TVN channel he saw something “blue and white passing close to my face, and it was like on one side and above me.

“I didn’t understand what was happening and then I sank. I thought it had eaten me.”

His father said he turned around and “didn’t see anything, I didn’t see Adrian”.

“That was the only moment of fear I really had, because I didn’t see him for like three seconds. And suddenly he shot out,” he told TVN.

Experts said the whale could never have swallowed the kayaker, as humpbacks have small throats.

“It seems that the kayak was right in the whale’s feeding patch (of krill or fish),” marine biologist Maria Jose Perez, of the University of Chile, told AFP.

That is why it is seen “emerging to the surface sideways, with its mouth open”.

“These events are very rare and have happened in the presence of silent vessels, such as kayaks,” she said, explaining that the whale probably did not notice the small boat.