For those of you who are ocean swim training please note that I have spotted a lot of Portuguese Man o War (called jellyfish but not actually of the jellyfish family) on South Shore this week so watch out for them and note that they have long tentacles below the water surface. They cause a very painful sting. See below from Wikipedia and how to treat stings.
For more on how to treat stings, from Wikipedia, read on :
Stings usually cause severe pain to humans, leaving whip-like, red welts on the skin that normally last two or three days after the initial sting, though the pain should subside after about 1 to 3 hours (depending on person). However, the venom can travel to the lymph nodes and may cause, depending on the amount of venom, a more intense pain. Venom effects may mimic an allergic reaction but this is not due to true allergy which is defined by serum IgE. There can also be serious effects, including fever, shock, and interference with heart and lung function. Stings may also cause death, although this is extremely rare. Medical attention may be necessary, especially if pain persists or is intense, the reaction is extreme, the rash worsens, a feeling of overall illness develops, a red streak develops between swollen lymph nodes and the sting, or either area becomes red, warm, and tender.
Treatment of stings
Stings from the Portuguese man o’ war may result in severe dermatitis, characterized by extremely painful, long, thin open wounds that resemble those caused by a whip, but are not caused by any impact or cutting action, but rather irritating urticariogenic substances in the tentacles. Treatment for a Portuguese man o’ war sting includes the application of salt water and hot water to the affected area.
Vinegar has been shown to inactivate undischarged cnidae on tentacles. Vinegar has also been shown to inactivate venom. Still there exists contention in the literature in that other isolated studies suggest that vinegar dousing increases toxin delivery and worsens symptoms of stings from the nematocysts of this species. Vinegar has also been claimed to provoke hemorrhaging when used on the less severe stings of cnidocytes of smaller species.