Ron Takeda and Tavis Boise were a few miles off the coast of Santa Barbara when they noticed the large mass trailing behind them.

“Tavis, is it a dolphin?” asked Takeda as he stood on his foil board, a specialized form of surfing, propelling himself through the waves. Boise, who was filming their run, recognized the question as an ominous sign – the veteran surfers are familiar enough with dolphins that Takeda should have recognized one immediately.

It was, they quickly determined, a massive shark in hot pursuit of Takeda. The creature followed him closely, its fin poking above the water, as he moved at about 10mph.

Boise captured footage of the experience that has since gone viral. In the video, the animal can be seen chasing Takeda for about a minute. Boise can be heard shouting “Don’t fall!” as his path diverged from Takeda’s, then: “Oh my God, it’s coming for you!”

The shark tailed the retired mechanical engineer for about five minutes before finally letting up.

The day had begun with promise. Takeda, Boise and a friend had waited for the wind to pick up on Saturday before taking off in the water near the University of California, Santa Barbara on a 20-mile run.

As they made their way through the water, Takeda heard something behind him and quickly glanced back. He spotted a big body, as long as 13ft, and it kept on him, following his every move.

“My god, it’s still in pursuit. It’s still happening. This is beyond comprehension,” Boise said. “That’s when we both start to panic.”

They had both encountered sharks before, but never in a chase and for such a duration.

Takeda focused on staying upright and keeping the board above the surface, he said, and opting not to dwell on the shark’s presence. There were moments he thought the animal had left before he saw it behind him again, but eventually it disappeared.

Meanwhile, Boise knew that Takeda would be able to stay up more easily and decided to stay put. He caught up with him a few miles later.

Takeda’s first words to Boise after the encounter were appreciation for the glorious conditions on the water.

“The first thing he said was ‘It’s really good out here,’” Boise recalled.

They shared the video with friends and experts at the National Oceanic and Atmospheric Administration, who agreed with their assessment that the creature was a shark, likely a great white. The footage was shared on social media by a friend and quickly got more than a million views, and a few questions about whether it was AI.

Takeda and Boise theorize that the foil on the board, which from below resembles a sting ray, might have hit the shark, initiating a game of cat and mouse. “Put yourself in the mind of the shark. Your prey just tapped you on the shoulder and ran past you,” Boise said.

They were awestruck by the experience but not discouraged. Boise titled his video “Friendly Shark Chase” in hopes of not adding to the demonization of the creature.

“It’s clear that shark chased us for a long time. I’m really certain it was just out of curiosity. It never touched us,” Takeda said.

They planned to head back out on the water on Thursday.

“We feel pretty confident that even if this happens again, we know what to do next time, which is don’t fall,” Boise said.