The video was filmed in a

river in Brazil's Mato Grosso do Sul state.

It shows Dutch biologist and Professor Freek Vonk swimming next to a wild giant 26-foot and over 200 kg green anaconda.

Freek Vonk said: "I have seen and filmed many different anacondas in my life - also huge ones - but this particular specimen was an absolute titan. I have never ever seen a snake this big in my life, although I knew they had to be out there. "

"We encountered this snake while filming for my Dutch family TV show ‘Freeks Wild World’, a show about nature and wildlife for children. I’m currently in the process of filming season 14 and have made over 250 episodes in the last 13 years. "

"We were filming this huge green anaconda female basking on the river bank when she suddenly but gently decided to glide into the water. I had my mask and small scuba tank with me so I instantly decided to go after her. What happened then was almost unbelievable. I was able to get so close that I could just stick out my arm and I could have touched her head. Of course, I didn't. I was completely into the moment. "

"I'm 6'5'' myself and I weigh about 100kg so I'm not a small guy but I was absolutely dwarfed by this huge specimen. She was four times my size so likely around 26 feet and her head was as big as mine. She must have weighed over 200 kilograms, maybe far more. "

"And the great thing was, she did not look too bothered by my presence at all. The occasional tongue flick to pick up scent of what was going on was all that gave away this giant snake even noticed me at all. She just went on doing her thing while I swam right beside her. "

"My cameraman and I were with this amazing creature on the bottom of the river for a good hour while she was scouting the river and cruising the riverbed. "

"I have seen some amazing things during my career as a biologist and TV-presenter. I travelled to over 100 countries and did many hundreds of expeditions but this experience instantly went right on top of the list of my most "jaw-dropping moments." Just talking about the experience sometimes gives me goose bumps."