Firstly, I think this is a GREAT forum post - like the idea that you’re harnessing the knowledge of the greater dive community to answer your questions!!! When I saw your photos it brought me back to my recent experience while diving in Saba... during one of my ascents up a mooring line I brushed up on several clear jellyfish tentacles (which type I have no idea) and instantly began to feel a burning hot pain on my left hand. After boarding the boat I mentioned this to one of our dive masters who advised that I pour vinegar over the area of contact. Doing so didn’t do much for the discomfort like I hoped and within several days the area became increasingly red and sensitive to touch. Within about 2 weeks the the burning and sensitivity lessened but the skin which came in contact w/ the tentacles began to scale and shed. This was just over one month ago and all noticeable signs of the stinging incident have lifted. I too was shocked and a bit alarmed about what was happening but I don’t recall the black dots on the bumps I noticed. Perhaps this was in fact a coral or another variety of jellyfish. Don’t fret too much unless the rash/sting area spreads; it’s mostly superficial. :) ~Chris