Bad sting from Man o' War

a few tentacles stung my fingers. When I turned to look at what was hurting me, a tentacle slid onto my right arm. When I turned towards shore, about 7 tentacles wrapped entirely around my waist. I ran screaming towards shore with a jellyfish head trailing 6ft behind me. The stings were red lines with a larger dot every mm. It felt like a red hot, 3in nail piercing my skin every mm along the red line. When I ran out of the water, many tentacles were streaming from me. Even vinegar did almost no good. I did not get itchy or sick like so many other man o' war victims. This was not the first time I had been stung by a jellyfish and I am guessing that I had become immune to the poison the previous time.