I noticed thousands of jellyfish in the Burrard Inlet last time we had a family boat trip to Silver Falls and Granite Falls. I did a little research and apparently this is mating season for Moon and Lions Mane jellyfish. So I grabbed some snorkeling gear and a GoPro, and jumped in ;)
Moon jellyfish are a little bigger than palm size, and the few Lions Mane jellyfish I saw were about double the size of a soccer ball with whiskers maybe 1.5-2 meters long. Feels a bit freaky jumping in to the water in the middle of the inlet where you don't see anything except water and many jellyfish around :)
There were also thousands of little thumb sized jellyfish in there, which I believe might be earlier stages of development, dunno.