You Might Be Swimming with Jellyfish in Michigan Without Even Knowing It

Recently someone shared a fact with me that seemed so unhinged, I thought they had to be pulling a prank on me. What if someone told you there were really jellyfish swimming around in Michigan lakes. Would you laugh them off, or assume they meant some exotic species escaped from an aquarium?

Well, it’s true. Michigan is home to a species of freshwater jellyfish, and they’re not part of some Great Lakes myth.

Hauntings, Folklore, and Urban Legends Surrounding Michigan's Upper Peninsula ⬇️

These little creatures are officially known as Craspedacusta sowerbii, originally came from the Yangtze River in China but have been quietly popping up in lakes and ponds all over Michigan for years. And while the thought of jellyfish might remind you of a few painful stings and saltwater scenes from your vacations down south, the freshwater variety here are quite different.

First of all, they’re very tiny. I’m talking, barely the size of a penny, maybe a quarter if you catch one in full jellyfish mode. In fact, you may have been around them in the past and not even known in, since most people wouldn’t even notice them unless they were really paying attention. Even then, they might mistake them for floating leaves or bits of debris if they don’t know what they are. But if you do spot one, it’s a crazy experience.

 One of my coworkers shared this photo with me of when he spotted them a few years ago:

Unlike their ocean cousins, these freshwater jellyfish are totally harmless to us humans. Yes, they technically have stinging cells, but they’re so tiny and weak that you wouldn’t feel a thing. They’re not hunting people, they’re hunting plankton.

What makes them even more interesting is that they’re not always in jellyfish form. Most of the time, they exist as polyps stuck to underwater surfaces, basically invisible. It’s only when conditions are just right—typically in the calm, warm waters of late summer, that they bloom into their recognizable, jelly-like form.

And You’ll find them scattered across the state in lakes from Kent County to Washtenaw. They’re considered an invasive species, but good news is they’re not wreaking havoc like some of the others we’ve dealt with.

So if you happen to see one of these tiny little dudes pulsing through your favorite Michigan lake this summer, don’t panic. They’re more of a strange little nature surprise than anything dangerous.