This is some kind of aquatic plant. The locals called it "seaweed" but Hunan is landlocked and hundreds of miles from the sea so I am sceptical. It was good though.
Above is a quote from @liuzhou, the rest are my words:
Is the No. 3 image some sort of preserved form of what you posted about in this dish from Hunan? You do realize you're driving me craz/y(ier) right?