Do you know what this is?

That, my friends, is a Lion's Mane Jellyfish. It is the largest known jellyfish in existence, and is largely considered the longest animal in the world, its tentacles recorded as spanning a longer length than that of a blue whale.

I spent an unhealthy amount of time on Wikipedia last night, so I figured I would share some of what I learned with you. It all started with me reading about the pokemon Tentacruel, when I happened across this line explaining the origin of the pokemon's design:

"Tentacruel is similar to the Portuguese man o' war, which is not a jellyfish but a cluster of polyps."

I found this to be interesting, so I linked to the Wikipedia article to read more. I had heard someone refer to the man o' war as deadly, so I decided to look into the toxicity of its venom. It turns out that the man o' war is not deadly; sorry to disappoint you. Several jellyfish, however, have nasty stings, and it is the box jellyfish that is notoriously deadly. Specifically, this little guy:

The Malo Kingi is a tiny animal that possesses some of the world's most potent venom.

Vinegar or saltwater should be used on a jellyfish sting. Urine and fresh water will only encourage the venom to release from the cnidocytes. So don't let that lifeguard pee on you no matter how much he wants to.