Like a whisp of vapor

I've have always been intrigued by jellies. They seem to be made of almost nothing at all, yet they go about their business in the oceans just like any other fish would. They can be rather hard to photograph - at depth using the strobes can make them look rather messy and detached and even in the shallows when using just natural light (as in this case), it is really hard to get the focus right. The trick is to use manual focus and just snap a ton of exposures while moving the camera back & forth.

I have not been able to ID this specimen. I thought the not-totally-but-somewhat-transparent tentacles looked rather curious, sticking out like that out of nothingness.