Wow that's an amazing story. They are beautiful creatures that get a bit of a bad rep.
I had to do a little research, it seems the Stomolophus Meleagris (or Cannonball Jellyfish) was most likely your saviour. Interesting as they are typically not a breed that would sting humans.
For creatures that don't technically have brains they somehow seem to know what's going on.
I'm pretty sure it was something a little more tentacly, I had a long zigzaggy pattern from where the tentacle stuck on me, and I had to pull part of it off. I was in a place called San Juan Del Sur and I just read on Google that other people have had that type of sting too there! It wasn't super painful, just enough to wake me up, felt like a little burn.
Ah that sounds like a sea nettle then. My favourite breed of jelly. I'd love to own one but my current tank is to small for them as they need more room for the long oral arms and the delicate nemocysts.
Wow cool, I wasn't sure what kind it was, since it was night I couldn't see much of anything in the water lol Which made the swim back to shore not so fun and pretty freakin scary! Won't be going swimming drunk in the ocean at night again, that's for sure lol