Dr. Solomon David, a fish ecologist at the Shedd Aquarium in Chicago, is a huge movie buff, looking forward to "Avengers: Age of Ultron," "Jurassic World," "Star Wars" and all of the other big blockbusters coming out this year. As it turns out, however, he’s made quite a small blockbuster of his own recently: "Leech-nado."

The one minute and 50 second clip features a squirm-inducingly large school of leeches swimming and wiggling through a Green Bay waterway. They’re almost graceful … if you can get past the overwhelming initial gag reflex. And unlike its kitschy, campy namesake, his freaky footage and the creepy crawlers doing their best Michael Phelps impressions are very, very real.

"This stuff actually happens, whereas we have still yet to see a cyclone of cartilaginous predators," laughed Dr. David.

Though he’s based in Chicago, Dr. David is currently working with UW-Madison on an initial three-year study of Great Lakes migratory fishes, seeing how aquatic creatures move back and forth between various ecosystems in the area.

"The point is those fish that move through different habitats can serve as environmental indicators as they move through checkpoints throughout the ecosystem," Dr. David said. "Knowing how many fish make it from, let’s say, the Great Lakes proper into a particular stream and then into a wetland, we can look at the numbers and judge how healthy the environment is overall and how restoration practices are making a difference."

For most of the public, monitoring fish movement in streams and culverts and analyzing data may not sound like the most scintillating sounding work. In order to make their work more available and accessible, Dr. David often carries around a small GoPro camera on his excursions to capture some of their more peculiar findings and share them on the Internet.

"I’m a firm believer in the science communication that using Twitter and video and the Internet can provide," Dr. David said. "It’s one thing to talk about what we do, and it’s great to get photographs of what we do. But if we can get video and show people – whether it’s the public or educators – I think that really opens up people’s minds to what’s out there and maybe right in your backyard. For people in the Great Lakes area, it is your backyard, and we should care about it."

About two weeks ago, Dr. David and his GoPro went out to the Green Bay site to drop in temperature recorders – a typical day – in an agricultural ditch wetland junction when he noticed he was unnervingly far from alone.

"I see these creatures swimming around there, and with more of a zoomed out inspection, they were just everything," Dr. David recalled. "I’d never seen that many (leeches), and here you are in this kind of isolated area. It’s kind of creepy with that sense that all of these leeches are everywhere."

The researcher was thankfully wearing waders, but still, he impressively didn’t instantly blood-curdlingly bound out of the water and begin shivering with "Stand By Me"-esque nightmares (he thanks previous work he’s done with parasites for making him familiar – if maybe not comfortable – with the slippery bloodsuckers). Instead, he did the next most logical thing: grab his GoPro camera and record the phenomenon. And after that, he still had to drop the temperature markers into the pool – requiring him to put his bare arm shoulder-deep  into the leech-infested water.

"You do what you gotta do to get the job done," Dr. David joked.

After finishing the job, Dr. David posted the creepy clip – with some extra ominous music to set the mood – to YouTube, where "Leech-nado" has become a minor viral hit, scoring almost 125,000 views.

"I knew I was doing my job when I posted it, and I had comments from people saying, ‘Ew, I just had my lunch!’ and, ‘This is really gross!’" Dr. David said. "I didn’t want to put people off from getting into the Great Lakes or anything like that, but to show that there are unique phenomenon going on out there."

But now for the important question: What does this flock of leeches mean? Are the Great Lakes in trouble? Will we soon be praising our new leech overlords? Soon after the discovery, Dr. David got in touch with Mark Siddall, a researcher from the American Museum of Natural History ("His handle is @theleechguy, so I figured this guy could probably help us out"), and while there’s plenty creepy about the swimming swarm, there’s nothing technically troubling or foreboding about it.

"I’d never seen anything like this before, and it seems to be a relatively unusual occurrence, but that could just be that people aren’t hitting it at the right time where they see it happening," Dr. David explained. "Our best guess right now is that it was a spawning aggregation. If the conditions are right, a bunch of leeches come out and spawn and then go back about their business of feeding and other stuff. What it means for the ecosystem is that these sorts of things happen all the time; it’s just a matter of if we see them."

"I would say this is a healthy thing," he continued. "What we’re seeing in a lot of these areas are sort of healthy, good indicators of ecosystem health. We’re seeing pike moving up into these systems, and they’re spawning and migrating. We’re seeing other native species moving into the system."

There’s even a good chance that these particular leeches were not of the bloodsucking variety. Dr. David and the team are hoping to get more samples to confirm this discovery; he returned to Green Bay Tuesday for research, and he’ll be back up and down continuing his work through the end of June. But like any good creepy horror movie villain, the leech pack has vanished without a trace.

"I sent my field team there a few days later to get samples once we found out this might be an important population from a conservation perspective or just simply unique, and they were all gone," the researcher noted. "A lot of phenomenon in the Great Lakes around this time of year are very ephemeral, so you’re there at the right time and see something crazy or bizarre, and a day later, it’s back to normal."

And on that note, have fun swimming this summer.