What Swimmers Need to Know About Jellyfish

Often, when nonswimmers find out I’m an open water swimmer, their first question is, “Aren’t you afraid of sharks?”

Frankly, no, I’m not terribly concerned about sharks because I tend to avoid locations where they may be more likely to congregate (near their preferred foods of seals, sealions, and schooling fish) and I know I’m not actually on the menu.

No, sharks don’t frighten me, but jellyfish—now, they haunt my nightmares. The brainless, gelatinous jellies that can wreck an otherwise great swim are the foe I prepare myself to face every time I swim in a marine location.

Here's what open water swimmers need to know about jellyfish.

Do Some Homework

If you know there could be jellyfish where you’re planning to swim, it’s a good idea to understand which species you’re most likely to encounter. Not all jellyfish stings feel or act the same way, and depending on the specifics, there can be varying recommendations for how to alleviate the sting.

For example, the Cleveland Clinic notes that applying vinegar or rubbing alcohol to the affected area is a good way to combat stings from many kinds of jellyfish, but “you shouldn’t use vinegar for Portuguese man-of-war stings,” the hospital reports. This is because vinegar “can cause more venom to be released from the nematocysts.”

It’s worth pointing out here that Portuguese Man ‘o War are not technically jellyfish; they’re a species of siphonophore, which are clusters of genetically identical entities that work together as a floating colony of pain. Nevertheless, their squishy corporeality and behaviors are similar to many other types of jellies and they can land a similar wallop, so they’re often lumped in with the 2,000 or so known species of jellyfish that clog the world’s oceans.

Avoidance is Key

As with most anything health related, prevention is always preferable to treatment. If you can avoid getting stung in the first place, that’s generally the best course of action.

To do this, avoid the places where you know jellyfish tend to collect. These brainless, spineless creatures drift on the tide and with currents and wind, so if you’re going to be swimming in a contained section of a larger harbor, for example, depending on local conditions, there could be more jellyfish there than at another nearby beach that’s facing open ocean or sees a stronger tidal flow to push these creatures along.

Any time you’re trying out a new-to-you swim area, it’s important to talk with local folks—swimmers, boaters, lifeguards, anglers, and other waterway users—beforehand to learn that to watch out for while you’re out there. Other open water swimmers will likely be able to tell you where jellyfish tend to collect and where else you can swim that may host fewer of the critters.

Some jellyfish species peak in the early summer while others prefer later seasons. Some rise to the surface in the evening, while others just drift around all day. This goes back to knowing the predominate species you’re likely to come across in a specific location and understanding how they behave and when they’re more likely to interfere with your swim sessions.

Protective Options

Wearing a long-sleeved wetsuit or a rash guard could help protect your skin from stings. In addition, products such as Safe Sea (a type of sunblock that contains jellyfish sting–blocking ingredients) may help to create a barrier between your skin and the jellyfish’s stinging cells.

In some parts of the world, jellyfish nets help keep swimmers safer—they catch jellyfish before they blow into the swimming area, keeping it clear and safer for swimmers. While these aren’t super common in most parts of the United States, you may find them encircling swimming beaches in Australia and other parts of the world where especially dangerous types of jellies may be present.

Treating Jellyfish Stings

If you’re stung by a jellyfish, it's generally recommended to rinse the area with salt water to remove whatever tentacles or stinging cells may be clinging to your skin. Avoid using fresh water, as this can trigger the release of more venom. You can also use the edge of a credit card to scrape off any remaining tentacles or bits.

Once you’re rinsed, you can try dousing the area in vinegar or rubbing alcohol or try soaking the area in hot water to help denature the protein in the venom that causes pain and irritation. You can also apply a topical steroid cream such as hydrocortisone or a soothing calamine lotion to help alleviate itching and irritation. Ice, an antihistamine such as Benadryl, and over-the-counter painkillers, such as Tylenol or Advil, may also help alleviate some symptoms.

Some swimmers, however, may experience an allergic reaction to a jellyfish sting. If this is happening to you or you’re having a very painful or severe reaction, seek immediate medical attention. Local lifeguards typically have some type of remedy on standby that can be used to address jellyfish stings, but you may also need to visit the emergency room, especially if you develop symptoms such as difficulty breathing, chest pain, muscle cramps, nausea or vomiting, or any other signs of a severe allergic response after a jellyfish sting.

And before you ask, no, don’t pee on the sting. That’s an old wives’ tale that has no scientific evidence to back its use. “In fact, peeing on a jellyfish sting could actually make the sting hurt worse,” the Cleveland Clinic reports. So, skip the pee, and head straight to the ER if you’re really struggling after a sting.