Done a lot of swimming in the keys, plenty of jellyfish, every now and then i got a little sting from one, it's kinda like getting bit by an ant or three, not a big deal, and despite my complete lack of aversion to them, this is still terrifying... :)
So actually this is a frame partway through the animation. I took it here because I quite liked it looking like a jellyfish :)
But actually once the animation fully plays out, all these threads come out the centre and it forms an iris. You can see it more clearly in this earlier version: