"I'm not sure who got more of a surprise: the seal, the octopus, or me," Mulinder wrote on Instagram in a comment about the video.
But what exactly was the sea lion up to?
For answers, we turned to two scientists who know something about what makes sea lions tick: Colleen Reichmuth, a principal investigator and associate research scientist at the University of Santa Cruz's Institute of Marine Sciences, and Peter Cook, an assistant professor of psychology at the New College of Florida who studies animal cognition and has experience with sea lions.
First off, they wanted to make clear that the pinniped in question was indeed a sea lion, not a seal. Cook guesses the star of the show might be a New Zealand sea lion based on the whereabouts, but he couldn't be completely sure from the video alone.
Sea lions and fur seals belong to the otariid family and are sometimes called "eared seals." Unlike true seals, however, they have external ear flaps and big front flippers, which allow them to be more active on land.
Behaviorally, Cook says, sea lions are more outgoing than seals and have a more flexible foraging ecology, meaning that they eat a wider variety of things — crabs, squids, octopuses, really anything they can get a hold of.
Sea lions also eat their prey in much less predictable ways.
It might be sea lions' tendency to play that gives them their complex feeding behaviors, Cook says. Sea lions spend anywhere from nine months to two years with their mothers before venturing out on their own. During that period, they are being fed milk by their mother and have a lot of free time, most of which they use to play.
"In animal behavior work, we tend to think of play as a way that an animal learns and sort of preps itself to take on a more complicated set of potential behaviors as an adult," Cook says.
So was the sea lion just playing with the octopus?
It's hard to say, Cook says, but it's possible. "They do like to fiddle with their food, and throwing an octopus around could be pretty fun," he says.
Cook says he has witnessed sea lions in captivity playing with leftover food after finishing a meal. For half an hour or so, a sea lion might throw a piece of fish up and down, playing catch with itself.
For Cook, a sign that this sea lion might have been messing around with the octopus is that after the smacking incident, the sea lion circles back, swimming very slowly. The way it turns and flops its flipper tells Cook that it's pretty relaxed, and sea lions are not usually relaxed when they're chasing down food.
At the same time, sea lions also sometimes throw their food around to make it easier to eat.
Reichmuth says the video could portray typical sea lion foraging. "The behavior in that video is pretty normal behavior for a sea lion that is feeding on prey that is too big to swallow whole," Reichmuth says.
Sea lions don't have grinding teeth, so while they can hold onto a slippery fish or octopus, they can't chew it well. Instead, they bring the prey to the surface and smash it on the water to break it into bite-size pieces, she says.
Reichmuth and Cook agree that it is entirely likely a feeding sea lion would have flung the octopus out of the water and smashed it on the surface, whether the kayakers had been there or not.
Sea lions typically regard humans with indifference. "They definitely will approach people and look at them, but they mostly just do their own thing," Cook says.
So it's unlikely the sea lion was using the octopus as a weapon to fight the humans, according to Cook. "The idea of a sea lion hitting a person aggressively with an object — I've never heard of that happening. I'd be very surprised," he says.
But even though sea lions can be indifferent toward humans, it doesn't mean they can't be bugged by us, Reichmuth says. "Sea lions are playful animals, but that doesn't mean they're not disturbed by the presence of people," she says, especially when they are carrying out biologically important activities like foraging for food.
The kayakers, she says, most likely paddled into an area where the sea lion was feeding, putting them in the line of fire. "You see the animal surface a few times, so [the kayakers] probably were not where they should have been, maybe a little too close to feeding animals," she says.
This makes her think that while the video is entertaining, it also evokes a larger issue: the encroachment of people into wildlife areas.
Common courtesy for wildlife, she says, is to stay well away from the "threshold of response," which is when animals alter their behavior because of human presence.
In the end, though, it's hard to know with certainty what the now world famous sea lion was doing with the octopus, or if its behavior was affected by the kayakers.
Anytime someone witnesses a novel sea lion behavior, or the unexpected actions of any behaviorally flexible animal, Cook says, there's often speculation about why it might have done it.
"Frequently people observe sea lions doing new things that we did not know they could do," Cook says. "There are always a lot of questions, and we make our best guess. But, yeah, they can surprise you."