Video captured by a tourist on board a boat in northern Botswana showed the heart-pounding moment the vessel had to outrun a charging hippo.

Oznur Bell, who took the video, was on the boat Sunday with her three children and a close friend as they traveled between camps during their stay in Botswana, she told NBC News.

“It was one of the most terrifying moments I’ve ever experienced,” Oznur said. “Once he started charging after us, the adrenaline was unbelievable.”

One of the journey’s guides, who was operating the vessel, spotted the hippo and slowed the boat in an attempt not to disturb it, Oznur said. The vessel had just come upon an elephant, and she had her phone out when the hippo appeared, she said.

“I happened to have my phone in my hand because I was filming it,” Oznur said of the elephant. “By pure luck, I never put my phone away, which is the only reason I was able to capture what happened next on camera.”

The guide quickly realized the hippo had been provoked despite his efforts, she said.

Oznur remembers the guide saying, “Hold on — we need to speed up now before he decides to come after us.”

She continued, “The moment we accelerated, we looked back and realized the hippo was chasing us.”

Her video, posted to her Instagram account, shows the massive mammal extending its head and upper body out of the water in a marvel of propulsion that looks similar to a human breast stroke. The boat created a wake as it sped off and its operator smiled nervously.

“You can actually see the smiles on the guides’ faces, not because it was funny, but because it was a smile of pure relief,” Oznur said. “For a few moments, every single person in the boat was genuinely worried.”

It was a rare moment Oznur said she was glad she captured the chase on video.

“Afterwards, the guides told us that although hippos are known to be extremely territorial, witnessing a chase like this is not something they see very often,” she said. “They said we had experienced a truly extraordinary encounter.”

Hippos, which are herbivores, are the third-largest land animal after elephants and white rhinos and can weigh as much as 8,000 pounds. Despite their mass, the mammals do know how to accelerate in water and on land.

“They have adaptations to their semi-aquatic environments allowing them to move swiftly on both water and land,” states the African Wildlife Foundation. “Their feet have four-webbed toes that splay out to distribute weight evenly and therefore adequately support them on land, and their short legs provide powerful propulsion through the water.”

The number of fatal encounters between hippos and humans are not known, but are estimated at a minimum of 500 deaths each year.

One of their biggest threats is human encroachment, according to the World Wildlife Fund, which lists the hippo as “vulnerable” but not endangered.

“I feel incredibly lucky that I happened to be filming,” Oznur said, “because otherwise this extraordinary encounter would have lived only in our memories.”