yeah have seen it before on here.
Thought it was a big sack at first then it seems to come to life WIERD !

I've never seen this before, that I can remember. With my limited knowledge of what lives in the oceans of the world, I would say it is a jellyfish of some sort. Or at least similar to a jellyfish. We all know that there are potentially thousands of undiscovered creatures in the ocean, and these probably comprise a large percentage of all undiscovered animals in total.