‘Tis the Season to Avoid the Stinging!

Jellyfish simply flow with the tide. Yet in the event you make contact with the tentacles of one you may feel it was a premeditated attack.

Each year we are visited by the infamous jellyfish. Some seasons we barely notice them while other seasons seem as though a full blown invasion is occurring.

Individuals react differently to mosquito bites, no-see-um bites and even the sting of a bee or wasp; jellyfish stings are no exception.  Divers have boarded dive boats with whelts on their legs complaining of terrible pain while others showing the same signs appear to be suffering from only mild discomfort.

The three most common types of jellyfish in the Keys are the Portuguese man-of-war, the moon jellyfish and the upside down jellyfish.

upsidedownUpside down jellyfish are found in shallow waters and common around mangroves. Cassiopea is the scientific name for the upside down jellyfish. It earned the common name due to the fact that it rests on the ocean floor upside down, allowing its tentacles to be exposed. Some say they look like flowers or cauliflower. The sting is not terrible; unless you have an allergy.


moon-jellyMoon jellyfish are normally pelagic but can be found in deeper waters as well. They can easily reach the size of a dinner plate. Their tentacles are only a few inches long. Some report the sting to be harmless. Speaking from experience, it depends on the location and severity of the hit. Brushing up against a moon jelly with the back of your hand isn’t so bad but if the tentacles land on the thin skin covering your inner wrist or your neck, that’s an entirely different pain.



manowarPortuguese man-of-war, which are not scientifically considered jellyfish but an invertebrate, are found on the surface. These guys are the ones to avoid at all cost. They can deliver a severe sting. They float on the surface allowing their tentacles to stretch out below them. Depending on the size of the man-of-war, their tentacles can grow several feet.

So, how do jellyfish cause harm?
It’s the tentacles of jellyfish that carry their arsenal. Once contact is made with the tentacles millions of nematocysts are released. Nematocysts penetrate the skin and inject venom. They are released with such force you may be behind an individual that has made contact with a jellyfish and suffer the wrath yourself.

It is not only in the beautiful waters that we need to concern ourselves with jellyfish. The beaches also need to be approached with caution. In the event a jellyfish is washed ashore and dead to the world, we still need to avoid the tentacles.

Exposure suits during the height of the season can be your best defense. The water is warmer during the moon jellyfish season but a thinner 1 mill or ½ mill neoprene wetsuit is a great barrier. Keep in mind that once a jellyfish brushes against your exposure suit, or any dive gear for that matter, stinging tentacles may be deposited. Take care when removing your dive gear not to touch any areas that may have been struck by a jellyfish.

Definitely keep an eye out as you begin surfacing from your dive. You’ll want to take time to check the water between you and the surface, your current depth and just below you. If you are conducting a safety stop or there is current, it becomes a bit more challenging to avoid jellyfish. Sometimes it appears they come out of nowhere popping up from underneath the diver below you.

What to do if you are a victim of a jellyfish sting? According to Divers Alert Network (DAN), flush the affected area with seawater to remove any remaining tentacles. Hot water is recommended as the best cure, over ammonia or vinegar. The heat from the water helps eradicate the stinging agents from your skin. Ammonia or vinegar may trigger unfired nematocysts. Avoid the fresh water rinse hose on the boat.

Seek medical attention immediately if you experience extreme swelling, difficulty breathing or have any suspicion of an allergic reaction.

Jellyfish are a part of the Keys and just like scorpionfish or lionfish, they do have the ability to cause pain. With a little care the stings may be avoided. They are not reason to fear the water.

On a different note, jellyfish are food for our turtles. Please keep that in mind and avoid littering our waters. Plastic bags resemble jellyfish in the water. Even though the bag is biodegradable doesn’t mean it is turtle proof!

Tracy Brenner has been a resident of the Florida Keys since 2002. Tracy owns and operates Abyss Dive Center in Marathon. Tracy’s scuba instructor rating is a PADI Course Director. She is an Instructor Trainer for Divers Alert Network and a Diving Safety Officer for the American Academy of Underwater Sciences.