The stinging cells in jellyfish contain nematocysts which house jellyfish venom. If you are unlucky enough to be stung, these nematocysts can be deactivated by rinsing with salt water or a solution of vinegar. If rinsed with freshwater, the delicate balance of solutes within and outside the nematocysts changes, causing these cells to release more venom. So can urine be used?

The specific gravity of urine, which measures how dilute urine is, changes depending on how well hydrated a person is. Because of this variation in urine concentration, applying urine to the affected area will upset the balance of solutes causing the nematocysts to release more venom.

What’s the solution? After rinsing with saltwater or vinegar, the nematocysts can be removed by applying shaving cream (what? you don’t carry this when you’re at the beach?) or a mixture of seawater and sand. You can the “shave” the area with a credit card or yes, the razor you just happened to have on you.

For more info on this, you can read the article published by Scientific American at the following link.