They have no brain or heart, can only swim slowly and are helplessly exposed to the ocean currents – yet they rank among the most successful animals our planet has ever seen: jellyfish.

While scientists are fascinated by these boneless creatures, most beachgoers do not take kindly to jellyfish. Especially in summer, the animals populate the entire Florida coast. Then, the chances of getting stung are high.

Yet how dangerous are jellyfish really? How can you prevent painful encounters, and what should you do in case of an emergency? We will give you the answers in this article, while also revealing more about the most common jellyfish species in Florida.

Jellyfish – important Facts

Despite their rather simple design, jellyfish form an extremely diverse group of marine animals. Here are the most important facts about jellyfish:


Jellyfish are among the oldest animal species and have been populating our planet for 600 million years. During this time, their physique has hardly changed, as fossils show. The animals have conquered a wide range of habitats: from cold oceans such as the North Sea to tropical waters. While most species swim near the surface, jellyfish are also found in the deep sea.

Characteristics and Size

Jellyfish are invertebrates. Their bodies consist of a gelatinous umbrella with an opening for feeding and excretion on the bottom. Depending on the species, short or long tentacles extend from the body. These are equipped with nettle cells that deliver venomous stings when touched.

The size of jellyfish ranges from less than finger-sized species to the Japanese Nomura´s jellyfish: true giants that can grow up to 6.5 ft in diameter and weigh 440 lbs.

Behavior and Diet

Jellyfish move through the water by contracting and expanding their umbrella muscles. This method of transportation relies on the recoil principle and is extremely energy-efficient. However, it is also slow, and jellyfish are exposed to the ocean currents. In coastal waters, the animals often wash up on beaches. Some species, such as the Portuguese man-o´-war, do not move actively, but use their gelatinous sails to float on the ocean surface.

In any case, their behavior makes fast movements superfluous, as most jellyfish catch prey with their tentacles. These are almost invisible, can be several feet long and feature venomous stinging cells. Depending on the species, jellyfish feed on plankton, fish, eggs, crabs or other jellyfish.


Jellyfish not only have a highly complex life cycle. The animals can also reproduce both sexually and asexually. Free-swimming female jellyfish produce eggs that are fertilized by the males – usually without physical contact. Emerging from the eggs are polyps that anchor themselves firmly to the seabed or rocks. Once the polyps have reached a certain size, they emit small jellyfish without the help of a sexual partner. Thus, the reproductive cycle begins again.

Distribution in Florida

Jellyfish are found in all coastal waters of Florida. Particularly affected, however, are the Atlantic coast and the northwestern Gulf Coast, also known as the Florida Panhandle. In the warm waters around the Florida Keys, the animals are also native. Slightly fewer jellyfish populate the southern Gulf Coast from Tampa to Marco Island.

Jellyfish Season in Florida

Jellyfish can be found off the coast of Florida all year round. However, there are times when the animals appear more frequently. Jellyfish Season usually lasts from May to October, and peaks in August or September.

Recently, marine biologists have registered an increase in the jellyfish population. With warmer seawater, the number of microorganisms such as plankton increases, and with it the food for jellyfish. This could lead to the Jellyfish Season starting earlier in the future.

Jellyfish in Florida – common Species

Jellyfish are found in all coastal waters of Florida. Particularly affected, however, are the Atlantic coast and the northwestern Gulf Coast, also known as the Florida Panhandle. In the warm waters around the Florida Keys, the animals are also native. Slightly fewer jellyfish populate the southern Gulf Coast from Tampa to Marco Island.

Moon jellyfish (aurelia aurita)

This jellyfish species lives in all oceans – preferably near the coast, where there are moderate currents. Its flat 8–12” umbrella is slightly curved and has a white to yellowish coloration. Moon jellyfish mainly feed on plankton. They only have short tentacles, are non-venomous and do not pose a threat to humans.

Cannonball jellyfish (stomolophus meleagris)

This dome-shaped jellyfish with light brown or bluish coloration can grow up to 10” and does not have long tentacles. Nevertheless, its body is covered in sting cells, which is why you should never touch dead specimens. On contact, the sting cells cause a burning pain and redness of the skin. They can also lead to the so-called Irukandji syndrome, which manifests itself in the following symptoms:

  • Severe pain in the back, abdomen and extremities
  • Nausea and vomiting
  • Perceptual disorders and feelings of anxiety.

In the worst case, death from pulmonary edema or cerebral hemorrhages can occur.

Atlantic sea nettle (chrysaora quinquecirrha)

Sea nettles can be easily identified by their 10–16” umbrellas with brown stripes. They populate the tropical and subtropical waters of the Atlantic, where they hunt small animals and other jellyfish with their venomous sting cells. Upon contact, these stingers cause a painful rash that usually lasts for 20 minutes. Deaths, however, are extremely rare.

Box jellyfish (chiropsalmus quadrumanus)

This jellyfish has an umbrella that measures up to 12” in size, is almost transparent and box-shaped – hence the name. Extending from the body are up to 13 ft long tentacles, with which the jellyfish kills its prey. The animals are difficult to spot due to their camouflage. Fortunately, the species found in Florida is less venomous than its Australian relatives. The bad news: Getting stung still causes severe pain and can lead to cardiac arrhythmias as well as respiratory problems.

Portuguese man-o´-war (physalia physalis)

Strictly speaking, this bizarre-looking animal is not a jellyfish, but consists of several symbiotic organisms. A most striking feature is the gelatinous, blue sail used for moving on the ocean surface. Underneath, up to 33 ft long tentacles extend from the body. These tentacles cause severe pain when touched. However, deaths are rare in healthy adults.

The Portuguese man-o´-war is mostly found in calm, warm waters – around the Florida Keys, for example. Especially in the winter months, you should exercise caution there, and do not go swimming near blue, gelatinous bodies in the water.

By-the-wind-sailor (velella velella)

Jellyfish are found in all coastal waters of Florida. Particularly affected, however, are the Atlantic coast and the northwestern Gulf Coast, also known as the Florida Panhandle. In the warm waters around the Florida Keys, the animals are also native. Slightly fewer jellyfish populate the southern Gulf Coast from Tampa to Marco Island.

Jellyfish in Florida – Tips and Precautions

Encounters with jellyfish can be extremely painful and, for certain people, even fatal. In order to avoid this experience, you should heed the following tips and precautions:

  • Pay attention to the official warnings. If there are signs on a beach that warn of jellyfish, you should be careful in the water. This is especially true for remote beaches without lifeguards.
  • On guarded beaches, you should pay attention to the purple flag, which signals dangerous animals in the water.
  • Stranded jellyfish are a sure sign that there are more specimens in the water. Especially when the wind blows inland, the animals are often driven into shallow areas.
  • The stinging cells of jellyfish can remain active long after the animal’s death. This is why you should never touch them with your bare hands.
  • Important for divers: Do not touch your face with diving gloves after stepping back on land. Otherwise, sting cells remaining on the glove could get in contact with your skin.

Jellyfish Stings – Symptoms and Treatment

Getting stung by poisonous jellyfish can be very painful. Victims compare the feeling to a continuous line of bee stings. After a few hours, the pain usually subsides, and a strong itching sensation remains.

To alleviate the symptoms, you should take the following measures:

  • Wash the wound with salt water – but not with fresh water, as this can prompt remaining sting cells to release more venom.
  • Treating jellyfish stings with urine is a widespread but unfounded myth. Instead, experts recommend mild acids such as vinegar in combination with warm water.
  • Afterwards, remove the visible sting cells with tweezers. You can also take a flat item (e. g. credit card) to carefully scrape off the skin.
  • To alleviate the itching, you can apply common insect bite remedies such as benadryl or cortisone.

How to deal with severe Jellyfish Sting

The symptoms of a jellyfish sting can also be more severe: for example, if large areas of the body are affected. Then, the unbearable pain could impair your ability to swim. You must get out of the water immediately or reach out to other people for help.

Follow this rule of thumb: If the combined streaks caused by the jellyfish are longer than 19 ft (6.5–13 ft for children), these life-threatening symptoms may occur:

  • Nausea and vomiting
  • Breathing difficulties
  • Shock
  • Cardiovascular problems
  • Heart failure.

The person must be taken to the hospital immediately.

Watching luminous Jellyfish in Florida

Encounters with jellyfish are mostly involuntary and painful. However, some tourists travel to Florida to see a particular kind: the rib jellyfish. This species has no poisonous sting cells. Instead, it scares off predators with the help of bioluminescence.

In the winter months, you can see this spectacular lightshow in the Indian River Lagoon near Orlando. There, rib jellyfish populate a mangrove lagoon, and guided kayak tours are offered. With a bit of luck, you can also see the jellyfish while wading in shallow water – e. g. at Kelly Park East, Cocoa Beach and Cape Canaveral.

FAQ – Frequently Asked Questions

When is Jellyfish Season in Florida?

Jellyfish find a lot of food in warm sea water. This is why the summer months are the main season for these animals. Since most tourists also travel to Florida´s beaches in the summer, many accidents occur during this time.

Can you touch moon jellyfish?

Feeding on plankton, this 8–12”, white-yellowish species does not feature long tentacles. Their sting cells are not large enough to pierce human skin. Therefore, you can touch moon jellyfish with no problem.

Are there Portuguese man-o´-war in Florida?

Yes. These jellyfish relatives with the striking blue sail live off Florida´s coast. Sometimes, they are also washed up on beaches. Since the sting cells of the Portuguese man-o´-war remain active long after death, you should never touch these animals.

Are jellyfish in Florida dangerous?

The stings of venomous species can be extremely painful. However, for healthy adults, they are rarely deadly unless large areas of the body are affected. The most dangerous species are box jellyfish and cannonball jellyfish.

Are there poisonous jellyfish in Florida?

Florida is home to both non-venomous and venomous jellyfish. The latter include, among others, Atlantic sea nettles, box jellyfish, by-the-wind-sailors and cannonball jellyfish.