How Fatal is A Box Jellyfish Sting? Box jellyfish, belonging to the Cubozoa class, are the world's most venomous sea creatures with up to 15 tentacles containing 5,000 stinging cells that release a toxin inflicting speedy blood pressure spikes and coronary heart failure. The Australian field jellyfish is especially deadly, with its venom able to inflicting excruciating ache, vomiting, complications, anxiety and potentially demise if left untreated. Box jellyfish actively hunt prey using their advanced nervous system and swim at speeds of 4 mph (6 km/h), primarily focusing on shrimp and small fish in tropical and subtropical waters. If sharks can have a week of their own, why not jellyfish - especially the hyper-venomous box jellyfish? Also known as sea wasps and marine stingers, box jellyfish belong to the Cubozoa class which incorporates 50 described species. A field jelly can have as much as 15 tentacles with about 5,000 stinging cells, often called cnidocysts that it makes use of to kill prey. How Fatal Is a Box Jellyfish Sting? While the stinging cells of different jellyfish can harm fairly unhealthy, the box jellyfish has a robust venom that may kill you - and make that process as painful as attainable. The Australian box jellyfish (Chironex fleckeri), is so poisonous that if one in every of its 6-foot-lengthy (1.8-meter-lengthy) tentacles touches you, it's possible you might die earlier than you attain the shore. The Lilliputian jelly (not technically a box jelly but still gnarly), Carukia barnesi, may have you begging to die because the ache, vomiting, headaches and anxiety are beyond excruciating. Occasionally fluid will fill the lungs and, if left untreated, may result in death.