Looks like the Lions Mane jelly, we get quite a few each year on the North East coast too. The stinging tenticles can stretch out about 10m behind them in a huge cone shape, not any worse than stinging nettles, for me anyway.
The folklore remedy is to urinate on the sting, to sooth it I guess. When scuba diving your likely to get stung on the lips as it's usually the only exposed bit of skin, I've always opted out of having my buddy p*ss on my face....
I say 'fishing' but morning fog rolled in so we mooched around the Harbour avoiding shipping for 2 hrs waiting for it to lift. Had planned to dredge for oysters, fish for blue cod and dive for paua (abalone)...
After we pulled the boat out we drove up the hill to see how thick the sea fog was, was pretty dense...