How can I treat a jellyfish sting?

First of all, you should try to avoid a jellyfish sting altogether by wearing a wetsuit. If you are stung, it is important to get out of the water as quickly as possible as jellyfish catch their prey by firing off small bags of venom called nematocysts.  Once out of the water, it is important to remove any remaining jellyfish tentacles to avoid additional toxins being injected into the skin; this is best done with ordinary household vinegar.  Pour the vinegar over the affected area and on any nematocysts and tentacles. If no vinegar is available, urine can be used due to its acidity and warmth. After vinegar or urine is applied, using gloves to avoid being stung, remove tentacles, and then apply a simple analgesic and some calamine lotion.