Some Aquariums Have Display Of Live Jellyfish,

and indeed some aquarist keep them as pets, 

above Diana when we were on Holiday in Bournemouth, 

also jellyfish have been mooted as food for us, as in this article from 2017, there is basically way too many of them, so the article argues that we should eat them to reduce their numbers, 

but could you eat one of these, a Portuguese man-o-war? (Physalia physalis), while the man o’ war’s sting is rarely deadly to people, it is intensely painful if you are stung by one and causes welts on exposed skin, also be warned the man o’ war may still sting you even weeks after having washed ashore, so why would you want to eat one or more? Well popular Japanese YouTuber ‘homosapi’ (ホモサピ) did, posting a video of himself cooking and eating a broth made with dozens of man-o-war jellyfish for his over one million subscribers, after seeking out a beach where man-o-wars were known to be washed ashore, he and his friends went there and picked up some of the blue balloon-like creatures, after washing them thoroughly, the YouTuber got to cooking, boiling the man-o-wars in water until they dissolved into a jiggly mass. He then cooked that jelly over an open flame for a few seconds before combining it with some veggies, sauces and what looks like MSG. He proceeded to eat the unusual dish and claimed it tasted a bit like scallops. He also reported no negative side effects, 

while man-o-wars can technically be consumed, by boiling them long enough for their protein-based toxin to be neutralized, it is still very dangerous. If the cooking time and temperature are not long and high enough, respectively, the protein poison may not completely lose its toxicity, Shuhei Ikeda, a jellyfish breeder at the Kamo Aquarium in Tsuruoka City, said that there is also a danger that the poison be inhaled via the fumes while cooking the man-o-wars. Even if not fatal, eating them can cause serious allergies and breathing problems, Homosapi advised his viewers not to emulate his stunt, revealing that he had a health professional supervising him the entire time he interacted with the man-o-wars, just in case something went wrong, well it might be helping to reduce the jellyfish population, but as far as seafood is concerned I will stick to fish & chips! as it happens he has so many videos about eating seafood, crustaceans and other fishy things, have a look here.