Cue the theme song. You know the one — the one with all that foreboding bass, the one that kids who haven't seen the movie like to hum when they're splashing at the beach and pretending there's a deadly predator nearby. Shark Week, by far the most popular week of programming on the Discovery Channel, is lurking, ready to chomp down on the nation's TV screens again this week. And that means David Shiffman is sharpening his harpoon. Shiffman, 29, is a graduate student at the University of Miami. He hasn't earned his Ph.D. nor written any books. But thanks to his savvy use of social media, Shiffman has become one of the most prominent shark biologists in the world — "which," he says, "is crazy. I'm definitely not the most knowledgeable person about sharks." But Shiffman's Twitter account, @WhySharksMatter, has attracted more than 17,000 followers. He's been interviewed by CNN and National Geographic and written for Wired and Slate. He was consulted by the makers of Sharknado 2: The Second One. He did an "ask-me-anything" on the Reddit website that drew 600 questions in three hours. And he is by far the most vocal critic of Shark Week, repeatedly poking at its producers with the sharp edge of his wit as he points out when the channel broadcasts "facts" that aren't. "The things they say are just nonsense," he said. Shiffman grew up in Pittsburgh, far from the ocean. But he was one of those kids who loved sharks and dinosaurs. He never got over his fascination with sharks. "They're a really powerful and in many ways a graceful and beautiful animal," he said. Because his grandparents lived in Boca Raton, the young shark fan spent five summers at Sea Camp in the Keys, eventually becoming a teacher there. That led to a career in marine biology, a degree from Duke University and graduate studies on Australia's Great Barrier Reef before he landed in Miami. He has spent hours in the ocean tagging sharks to study their travels. "People think of sharks as mindless killing machines," he told his Reddit audience, "but they actually have larger-than-expected brains for their body size and lots of complex social and ecological behaviors." He can't remember how many times he's seen the original Jaws. "It's a great movie, as long as you understand that it's totally fictional," he said. And he says he's watched every episode of every year of Shark Week. That's why he's so disappointed with what it has become. Begun more than a quarter of a century ago, Shark Week is the longest-running cable TV programming event in history, drawing nearly 30 million viewers. It has become a pop culture phenomenon, joked about on 30 Rock and declared a holy occasion by Stephen Colbert. You can even buy Shark Week merchandise — T-shirts that say "Bite Me," shark beach towels, shark slippers, a shark fin statue for your pool deck and even a book called Shark-Tastic! But somewhere the focus on educating the public about sharks fell by the wayside, Shiffman contends, replaced by shows that play up bloody attacks on humans and stories that are based on outlandish tales. "It used to be looked at as this cool thing," he said, "but then about 10 years ago they started getting into this shark hysteria. Now it's more like a horror movie." The low point came last year, when Shark Week kicked off with Megalodon: The Monster Shark Lives. The show claimed a gigantic species of shark that's been extinct for thousands of years was still swimming around, ready to chomp on unsuspecting humans. "That was about the last straw for me," Shiffman said. A Discovery Channel spokeswoman said producers are aware of Shiffman's concerns, and even credited him with inspiring them to do a show on bioluminescent sharks this year, adding, "While we may sometimes disagree on approach, the important thing is we use this as a platform to get the word out about sharks, which @WhySharksMatter does very effectively." He had more luck with the producers of the over-the-top SyFy movie Sharknado, persuading them to use some of their promotional time for their corny sequel this summer to also promote the cause of shark conservation. They even paid for some of his lab's shark-tagging work. Shiffman's influence may exceed his expertise, but what he's doing is worthwhile, said George Burgess. As longtime director of the Florida Program for Shark Research at the University of Florida and its International Shark Attack File, Burgess knows his sharks — and knows that last year there were 72 unprovoked shark attacks on humans worldwide (23 were in Florida, the shark bite capital of the world). "He's doing a good job of sharing with the world the work we've all been doing," Burgess said. When he was at Duke, Shiffman roomed with Andrew David Thaler, who launched a blog called "Southern Fried Science." Shiffman has blogged on the site since 2008, Thaler said, and "his work is consistently among the most linked and commented articles on the blog and has, over the last few years, won several awards." A year later Shiffman joined Twitter, taking the handle "Why Sharks Matter" from the title of the book he intends to write someday. For now he's got a dissertation to finish on how sharks affect the food web, as opposed to how fishermen, conservationists and scientists think that sharks affect the food web. He is cautiously optimistic about the future of his favorite sea creature. Recent studies have found that since anglers were banned from landing them, great white sharks in the Atlantic and Pacific oceans are rebounding. Meanwhile, Shark Week is showing "documentaries" such Shark of Darkness, about a 30-foot great white terrorizing South African shores for decades. "A 30-foot great white?" Shiffman tweeted last week. "Nope. Not real." Times researcher Caryn Baird contributed to this report. Craig Pittman can be reached at [email protected] or follow @craigtimes.