Thats a huge jellyfish... one of the things that I fear in the ocean are jellyfishes... although I like to scuba dive, I really don't want any close encounters with jellyfishes, whether they are huge or tiny..
anyways, do you guys believe that a cure to a jellyfish's sting is urine?
I was once stung by a jellyfish, but after I read the article, "fortunately" I it didn't happen in Japanese waters. The size of the creature was comparable to human fist, so once again "fortunately" I shook my hand probably with a jellyfish-child. The whole experience had a place in Egypt, so if by some coincidence someone is going there for a vacations, be aware, it hurts a lot.
PS. and don't urine on the part of your body where jellyfish has stung you, just buy some good medicine (preferable in form of a unguent) before your first dip