Are jellyfish deadly, can they be really dangerous?

Yes, they can be dangerous. The box jellyfish can kill a person under 70Kg in 3 minutes!

Some species of jellyfish are, but many are not. They can all sting, but for many species this sting actually has no effect on humans.

Different jellyfish have different strengths of venom. For example, the Box Jellyfish’s sting can cause quick cardiac arrest and has been named as the world’s most venomous creature. So yes, some can kill but others can’t

they are venomous (that’s why they are dangerous) and some types of jellyfish do kill people. the harmful jellyfish have stingers that are capable of piercing the skin and the venoms contain a variety of toxins which trigger many allergic reactions. so a person could die from an allergic reaction orrr anaphylactic shock

not all of them are, but some of them are deadly yes,as patricia mentioned, the box jellyfish is one of them

some are worse than others. the different types vary on how dangerous they are. some types will just hurt a tiny bit if they sting u, while others will be very painful, and some are very dangerous. if it is a minor sting (not dangerous) a good way 2 stop the stinging/pain is 2 have sum1 pee on it. sounds gross, but it helps. or other liquids high in acidity will work, such as lemon juice or vinegar :)