The sting of the Sea Nettle can be extremely painful, and the string from them can leave you with a painful rash on the skin for around an hour. The lion’s mane jellyfish is the largest species known to man, and the sting itself can be highly painful, and many sources describe it as being potentially fatal.
The blue bottle jellyfish has a painful sting that is characterized by a whip across the skin. The main risk is from systematic effects of the venom. The Irukandji jellyfish lacks in size it makes up for in the power of its venom. Box jellyfish are the most poisonous, deadliest and meanest of all the jellyfish.