Craspedacusta sowerbii)occurring in Ontario. I was not so surprised to learn that they are an invasive species that found it's way from Asia to North America some 100 years ago. My interest in these guys came about a few weeks ago when I got a phone call from a friend in Port Dover. He had a video of a jellyfish that his friend had found in Black Creek in Port Dover. Anyways, the video is pretty grainy but it clearly shows a small jellyfish just blobbing along like they do. From what I've been able to glean from the internet it seems like they prefer warm, still-moving water, are pretty small and aren't dangerous to people. They probably have a negative impact on the environment but I guess it can't be too bad (relatively speaking) since they haven't got the sort of press zebra mussels and other invasives have gotten.