Went SCUBA diving a few years ago off the NC coast. We had to get through a layer of jellies to get to the submarine we were diving on. The ONLY past of me that wasn't covered was the area around my lips that my regulator didn't cover. Guess where I got stung?!!!
I later bought an ice guard for my regulator mouthpiece to correct that deficiency!
Any local dive shop has little packets of gel made specifically for treating jellyfish stings. They aren't expensive and don't take up much room in a PFD pocket if you fish in an area where that might be a concern.