The animal swims closer to the dock after grabbing a piece of food that someone threw.
It then rises from the water toward a little girl kneeling near the dock, then goes back in. The girl and others laugh.
She sits on the dock. After just one second, the sea lion jumps back, swiftly grabbing the girl by her white dress and dragging her into the water. Onlookers can be heard screaming in horror. A man immediately gets into the water to save the girl.
Neither the girl nor the man was injured. She can be seen immediately leaving after the incident at Steveston Fisherman's Wharf near Vancouver, B.C.
The video, taken by Michael Fujiwara, was posted on YouTube on Saturday and has garnered 1.5 million page views as of Sunday afternoon.
"They were pretty shaken up," Fujiwara told CBC News. "Her family was just in shock."
Fujiwara said he goes to the dock regularly but has never seen anything like what he captured in the video. It's unclear whether Fujiwara and the man who jumped into the water know the girl. Fujiwara did not respond Sunday to a request for comment.
Andrew Tites, director of the University of British Columbia's Marine Mammal Research Unit, criticized those who got close to the animal, which he said is a California sea lion.
Tites said it's likely that the sea lion thought the girl's dress was food. Such animals, he added, are not naturally dangerous.
Attacks by sea lions on humans are rare, Lt. John Sandmeyer told a local television station in San Diego, where a sea lion dragged a 62-year-old man off his boat and about 20 feet underwater. Dan Carlin was posing for a picture with a yellowtail fish he had caught when the sea lion bit into his hand and pulled him overboard, the TV station reported.
Carlin survived the 2015 incident, but his hand required 20 stitches.
An adult California sea lion is about the same size as a 6-foot man and weighs about 610 to 860 pounds.Though the "cliched circus seal" that balances a ball on its nose and jumps through hoops is typically a California sea lion, such animals once in the wild are sleek and faster than any other sea lion, according to a National Geographic article.
They live along North America's western coast. Males migrate north during the winter season and return to the California and Mexican coastlines during the summer to breed.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)