Animal Planet's most-popular series, "River Monsters," was renewed for an eighth season before it even started its seventh season in early April. So it's no surprise its latest season premiere was the most-watched premiere (in live+3 ratings) ever on the network.

The show follows Jeremy Wade, an "extreme angler" as he travels around the world, searching for and learning about scary and dangerous aquatic creatures that may or may not be killing people. Episodes are framed as murder mysteries, so it's basically aspiring to be "Animal Planet"'s NCIS, as the network's president, Marjorie Kaplan, once told me.

Why is it so popular? Let's look at clips from last season -- and a few from this season -- to see just what the appeal of "River Monsters" and its host is.

Jeremy Wade does insane and stupid things
In his quest to discover things and/or make dramatic television, Jeremy Wade often does inadvisable things. His British accent and inquisitive approach make them seem less dumb than they may be, but he still does them. Here, for example, he walks around in the giant nest of a fish, the arapaima, that might not appreciate someone walking around in its nest.

Jeremy Wade is relentless in his pursuit of myths
In this clip, Wade catches a fish after making "over 13,000 casts," he says. That's commitment. The Canadian muskie he catches ends up being four feet long and powerful, and he explains why it -- or several of them swimming together -- might be mistaken for a Loch Ness-like monster roaming through a lake. "River Monsters" definitely bleeds myths and stories for all the drama it can, but often ends up being more like "Mythbusters" by disclosing what's really behind the stories.

There can be as much tension as "Jaws"
The editing on "River Monsters" is more like a horror movie or an action drama than you'd expect from a show about fish. Like Animal Planet's terrific reality TV show "Whale Wars," the series creates as much tension as possible with its editing. Even if things turn out to be innocuous or not that dangerous, the editing plays them up. Consider this clip, when Wade swims around in SCUBA gear looking for an anaconda and shares in a voice over, "the last thing I want to do is startle one and provoke an attack." That's followed by footage of murky water and the horror-movie thrills of the possibility that one could swim from the silt at any moment. When he does discover a 20-foot-long anaconda, it doesn't attack, but the show sure has ramped up the tension as if it might.

It's bloody and gross
A boy with a missing finger, the jaw of a fish that dug into a man's knee leaving a wound that took a month to heal. These are the stories in this clip, just some of many that show the occasionally brutal effects of humans' interaction with nature. The reenactments of deaths supposedly at the hand of these "River Monsters" can be gruesome, but it's the real-life footage that carries the most weight because it's, well, real.

If that's not gross enough, it can get grosser
In this clip, a doctor whose uncle drowned catches fish and examines their stomach contents. And yes, he finds pieces of his uncle's skin inside, which "River Monsters" shows via several pictures.

Local knowledge
"River Monsters" is not "Parts Unknown" or Anthony Bourdain's previous series, "No Reservations." That is, it's not focused on immersion in local culture that is educational and entertaining. But sometimes Wade's investigations, such as they are, involves learning from locals. Here, he learns from a local fisherman that the best bait comes from a small nut. Inside is a juicy worm, reminiscent of those that became a famous season one "Survivor" eating challenge.

You just may learn something
Again, yes, this isn't a typical nature documentary that puts knowledge and information first. Animal Planet reality series are now more about people than animals. But there is information. Here, for example, we learn about electric eels, with graphics that show how they deliver their charge and why eels don't wrap themselves around prey like some snakes do.

The mystery of what's at the end of the line
As an "extreme angler," Wade often goes fishing, though the mystery of what he'll catch (and then release) is the real source of drama. As something thrashes on the end of his line, the question is: What is it? Here, in a tipsy canoe, Wade battles a fish. It ends up being a 250-pound arapaima -- 250 pounds! -- a massive freshwater fish that's been blamed for drowning some people.