The 51-year-old Rainer Schimpf was filmed with his legs hanging out of a whale's mouth.
He and others in a team of expert environmentalists were in the water.
Suddenly the whole world around me got dark and I felt enormous pressure around my waist, in the area of my weight belt.
Joking aside, with the Bryde's Whale known to grow to a length of 55 feet, Schimpf was extremely lucky to escape without harm. "I instantly knew it was a whale because there was a pressure on my hip which increased slightly to a point where it stopped, " he said.
"It was an interesting experience for me, but surely nothing I want to do again", he said. "I instantly knew a whale had grabbed me".
Sorry to Baleen On You: Whale Almost Swallows South African Diving Tour Operator
"Once you're grabbed by something that's 15 tons heavy and very fast in the water, you realize you're actually only that small in the middle of the ocean", Schimpf said.
It's hard to tell who was more surprised by the situation: the human or the whale.
"We swam back to the vessel, climbed up and checked if I and the camera were OK - no broken bones, no cracked ribs - so all was good", he said.
Out of the darkness a Bryde's whale shot up from the depths, jaws wide open. It was no fault of the whale.
Most of us have a cartoonish idea of what the inside of whale's stomach looks like thanks to Pinocchio, but diver Rainer Schimpf nearly found out what a whale belly looks like for real. "They are gentle giants, and it was just an accident".
The type of whale involved was a Bryde's whale, which is a baleen-feeder that eats mostly plankton.