If you had told me there were jellyfish swimming around Ontario lakes, I would have laughed.
Actually… that’s exactly what happened.
A couple of years ago, someone at Bon Echo Provincial Park mentioned there were jellyfish living in Joeperry Lake. I honestly thought they were pulling my leg. Jellyfish belong in the ocean, right? I laughed it off and didn’t think about it again.
Then one afternoon I was standing on the dock at Bon Echo Lake with a coworker, looking down into the crystal-clear water. Suddenly, I noticed something tiny drifting beneath the surface.
Then another.
Then another.
Before long, there was an entire cluster of miniature jellyfish gently pulsing through the water.
I was absolutely flabbergasted.
Yes—Canada Has Freshwater Jellyfish
As unbelievable as it sounds, freshwater jellyfish are real.
The species found in Ontario is called Craspedacusta sowerbii. They’re believed to have originated in Asia and have quietly spread around the world over the last century, hitching rides on aquatic plants, birds, and even boating equipment.
Unlike their saltwater cousins, they’re tiny—usually only about the size of a dime or nickel. Their transparent bodies make them incredibly difficult to spot unless the water is calm and clear.
Once you see one, though, you can’t stop looking.
Are They Dangerous?
Not at all.
Freshwater jellyfish do have microscopic stinging cells, but they’re designed for catching tiny plankton—not people. Their sting is far too weak to penetrate human skin, so they’re completely harmless to swimmers.
They’re more of a fascinating surprise than anything else.
Why Don’t We See Them More Often?
That’s part of what makes them so special.
Freshwater jellyfish spend most of their lives as tiny polyps attached to underwater surfaces where they’re nearly impossible to notice. The familiar umbrella-shaped jellyfish only appear when conditions are just right.
Warm water, calm weather, and late summer are usually when they make an appearance.
Even then, they may only be visible for a short period before disappearing again.
One of Ontario’s Best-Kept Secrets
It’s funny how many incredible things exist right in our own backyard that most of us never hear about.
We spend so much time looking for wildlife on the shoreline or in the forest that we forget to look beneath the surface of the lake.
Sometimes the biggest surprises are floating only a few feet away.
I still remember standing on that dock at Bon Echo, staring into the water in complete disbelief. If someone hadn’t pointed them out to me years earlier—even though I didn’t believe them—I probably would’ve assumed I was imagining things.
Now every late summer, I find myself peering into the water just a little longer, hoping to catch another glimpse.
Nature always seems to have one more surprise waiting.
Have you ever spotted freshwater jellyfish in Ontario? We’d love to hear where you found them. Share your story with us on Instagram and tag @keep.north.co.