I came up through a tunnel at Palancar caves once, when I looked up I had maybe six inches on each side of me for clearance through the tunnel vertical hole. It is lined with fire coral. I did not feel like backing up. I could not see the vertical tunnel exit lined with the coral only the light when I entered the tunnel shaft. I could see that I had enough to get out so I chose to use it. Once I was in the shaft to exit then I could clearly see the fire coral. That moment was one to start getting calm.
I slowly started my ascent it was about 10ft high. The journey took forever as I looked up and could not move, only use my lungs for ascent. I was enjoying this actually. Very fortunate the hole is litterly vertical. My head popped through and I was almost free. Then I made the mistake of moving my hand, my index finger brushed the coral. I had to remain still to get my legs clear. Very difficult to not become victim of reflex. Once through my finger felt like I had stuck it in a bees nest and left it there for a minute.
My finger became numb and painful at the same time. A difficult pain to describe. It stayed painful after several procedures described above. I can say that when I got stung with the Lion Fish at least that little sting went away after 3hours. The fire coral one lasted 3 weeks. It itched like mad also during the healing. I did not break out just could not get the nomats out.
I remember where the hole is, wont go there again. The tunnel was worth the pain though. I do have a warped sense of adventure.
I have also brushed gentley against coral in tight spots with bare legs, coral is very sharp, if one gets scratched by it, the coral can infect the site. I does not need to be fire coral. If one comes into contact with the fire coral ya know it right now, that's the difference. At least in my experience with skin contact this is the way it happened. I very, very seldom touch the coral or any sea-life as I know how litterly dangerous and poisonous most creatures are.
Except Pez Leon they gotsta go!