In this image made available Tuesday Dec. 3, 2013, The hand of Harrison Odjegba Okene stretches through the murky waters to reach a rescue diver as the diver's headcam video records the moment he becomes aware that Okene is still alive after nearly three days underwater. (AP/AP)

By now, you’ve probably heard all about the trending story of the week: Harrison Okene, a Ni­ger­ian man was rescued after spending three days in a pocket of air in a tugboat at the bottom of the Atlantic ocean with nothing to eat or drink except a bottle of Coke.

It’s an astonishing tale of survival. But if you thought this story sounded familiar, you’re absolutely right. Okene was rescued six months ago. So why is his story screaming from the headlines this week?

The easy answer is that a video was just released that shows the rescue unfolding, which pushed the story back into the spotlight, even though the news cycle for it had long-since passed.

It’s difficult to pinpoint the starting point on this particular clip’s road to virality. But, according to track-backs and some hat-tips, it seems to have originated with a posting on the video-sharing site LiveLeak. From there, it got picked up by several news outlets around the world, including the Daily Caller. The Associated Press gave it a boost when the news wire asked the rescuers, DCN Diving, to verify the video and release a longer version of it online. Once the AP story hit, it was only a matter of time before the story found its way onto the most-read lists, inboxes, Facebook pages and even front pages half a year after it happened.

The trickier question to answer is: Why? Why did a story that made such a small public impact in its first go-around get such a feverish second life?

Many people, you may not be so surprised to hear, have made a study of these things. That includes Jonah Berger, a marketing professor at the University of Pennsylvania’s Wharton School of Business. Berger, in his book “Contagious: Why Things Catch On,” has identified six principles that help things go viral: social currency, triggers, emotion, being public and practical value.

Some of those factors are easier to explain than others. For example, people like to share things that make them seem cool, solve a clear problem for them, or that they see a lot of other people sharing. Others viral items have catalysts — think Rebecca Black’s “Friday” video, which YouTube has said gets a traffic spike at the end of each work week.

Some things go viral after careful cultivation. The Kony 2012 video that seemed to everywhere last March shared several of the factors Berger identified, and also spread as a result of careful promotion to top tastemakers over social media networks. The Kony 2012 campaign asked high-profile people from U.N. Secretary General Ban-ki Moon to actress Angelina Jolie to help.

But in the case of this rescue, it’s emotion that’s almost certainly inspiring people to share the story with friends.

And the fact that there’s a video documentation doesn’t hurt. It’s no coincidence that services dedicated to virality, such as Upworthy and YouTube, are video-based. It’s one thing to read about a man trapped in a pocket of air for three days at the bottom of the sea; it’s quite another to see the person in that space partly covered by water and almost feel the walls closing in.

And as compelling as it is to read about a diver seeing what he thinks is a corpse’s hand, it’s more visceral to see that hand and to hear the shock in the rescuer’s voice when he realizes that the person attached to it is still alive. Now that smartphones have put video players (and video cameras, for that matter) into all of our hands, it’s much easier to get people to watch, share and spread compelling stories that way.

Yet, content alone doesn’t always kick things to the viral level. Even folks who seem to have cracked the code, such as the editors of Upworthy, say that luck still plays a big role in making something go viral. And if there’s anything that Harrison Okene has -- in spades -- it’s that.

Related stories:

AP: Nigerian man survives 3 days at bottom of Atlantic

Kony 2012: The anatomy of a viral campaign

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