It looks like jellyfish, it swims like jellyfish. I'm a software engineer not a biologist. I can call it "a thing". Just tell me where they come from and where they go ;-)
FWIW I had a sponge release what I thought were "eggs" and then I had those in my tank (mangrove refugium). They settled out into a big spider web then crashed I don't recall the time frame though,, sorry.