Whether you’re a resident or visiting, you might be interested or even concerned about the types of jellyfish in Florida.
It’s easy to think that the Florida waters are filled with deadly jellyfish. However, we’re going to see that, although it’s reasonable to be wary, most jellyfish you might come across only cause, at worst, a mild irritation.
We will help you identify which jellyfish you need to stay well clear of and those you don’t need to worry about.
What Kind of Jellyfish Are Found in Florida?
Jellyfish are found in almost all of the world’s oceans, and Florida waters are no exception. While you probably won’t see them all year round, it is pretty common to see jellyfish in coastal waters as waters cool after the hot summer.
Florida waters are home to almost every type of jellyfish. From tiny, translucent animals to larger creatures that travel along the ocean surface.
These include some that appear in large numbers during jellyfish season but are only a minor irritation, like the moon jellyfish, to those which are rarer and more dangerous, like the box jellyfish.
You might come across jellyfish floating out at sea if you participate in watersports, but most people see them washed ashore on the beach.
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9 Types of Jellyfish in Florida
We will take you through 9 types of jellyfish in Florida waters. Starting with probably the most common, not just in Florida but also worldwide.
1. Moon Jellyfish (Aurelia aurita)
The moon jellyfish is a true jellyfish seen close to the shore in areas including lagoons, harbors, estuaries, and beaches.
Unlike some jellyfish, the moon jellies are poor swimmers, and they drift along in currents in cool, warm, and temperate seas feeding on plankton.
A fully grown moon jelly is about 25–40 cm (10–16 in) in diameter. They are round and reasonably flat with a gentle curve to their edges. They have short, nematocyst-laden tentacles underneath to catch food.
Moon jellyfish range from almost completely clear to a blue-purple color. One of the most distinctive identifying features is the ring of four, five, or six small pink or purple circles inside their translucent bodies.
Moon jellyfish frequently appear in large numbers. However, you don’t need to worry as most people don’t feel any sting if they come into contact with them. If you do feel a weak sting, it usually only lasts for less than an hour.
Mass strandings of moon jellyfish occur in Florida annually, so it’s common to see these creatures washed up, particularly in the winter months.
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2. Atlantic Sea Nettle Jellyfish (Chrysaora quinquecirrha)
The Atlantic sea nettle is a relatively common visitor to the coastline of Florida and is one that you might see while boating.
The Atlantic sea nettle jellyfish’s mostly clear or cream-colored bell is typically around 12 to 18 centimeters / five to seven inches across.
Atlantic sea nettles are usually marked with a noticeable orange-brown striped pattern around the bell. These markings are particularly evident in specimens seen at the surface in the Gulf of Mexico.
Atlantic sea nettle jellyfish have pretty long stinging tentacles approaching 50 centimeters / 20 inches. They use these for capturing prey, including plankton, comb jellies, fish eggs, fish fry, crustaceans, and mosquito larvae.
If you come into contact with an Atlantic sea nettle, the tentacles can give humans a somewhat painful rash and burning sensation. However, typically this tends to subside in under a couple of hours.
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3. Cannonball Jellyfish (Stomolophus meleagris)
Underwater the cannonball jellyfish looks almost entirely round and is said to be about the same size as a traditional cannonball at about 25 centimeters / ten inches diameter.
Cannonball jellyfish, also known as cabbagehead jellyfish, seen in the Atlantic and Gulf of Mexico, are often colored around the rim with brown pigment. They have a short cluster of oral arms underneath their mouth for swimming and capturing food.
In contrast to many other jellies, the cannonball jelly is actually a good swimmer. They can be seen underwater on a scuba dive moving at a relatively reasonable pace underwater.
The cannonball jelly releases toxins from its stinging cells that will stun small fish in its vicinity. Fortunately, this doesn’t seem to affect most people, although you might feel a tingling sensation if you swam very close to one. It certainly doesn’t affect sea turtles who enjoy eating them
Contact with a cannonball will result in a sting and a rash in the affected area. Usually, this goes away by itself, but it might require hydrocortisone treatment. If you should be unlucky enough to get stung in your eye, you should seek immediate medical attention.
Cannonball jellyfish are often washed up on the beaches in Florida and beached jellyfish decompose relatively quickly. Freshly caught specimens are considered a delicacy in Japan, although it is vital to know how to cook them correctly.
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4. Mushroom Cap Jellyfish (Rhopilema verrilli)
The mushroom cap jellyfish has a bell said to be shaped like a mushroom, and we’d agree that there is some resemblance. The bell of the mushroom jelly can get pretty big at up to 50 centimeters / 20 inches in diameter.
The mushroom cap jellyfish comes in a variety of common colors. You might see them with the bell light looking yellow, blue, brown, white, pink, or green. There is often a light-brown pigment around the edge of the mushroom jelly, irrespective of the primary color.
This jellyfish doesn’t have tentacles. However, it has eight short brown arms underneath that pack internal stinging nematocysts to immobilize its planktonic food.
As the mushroom cap jellyfish don’t have external stinging cells, it is unlikely that you’ll suffer a sting even if one brushes you in the ocean. It would likely only be a very mild sting if you should be unlucky enough to touch the stinging cells within their bells.
The mushroom cap jelly is commonly found along the Gulf of Mexico coastline. It can even be seen in the Chesapeake Bay in winter.
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5. Mauve Stinger / Purple Jellyfish (Pelagia noctiluca)
The mauve stinger, also called the purple jellyfish, is a relatively small jellyfish seen on the Atlantic coast and in the Gulf of Mexico. This jellyfish is well-known as a pest species in the Mediterranean sea.
The jellyfish can have a mauve, pink or purple color across its bell and tentacles. The bell ranges between three and 12 centimeters / 1.2 to 5 inches across. The mauve stinger has four arms for feeding and eight long venomous tentacles, which the jelly uses to stun its prey.
Unusually, the mauve stinger has stinging nematocysts on both its bell and tentacles, so if you touch one, you will likely know about it. It is possible to get stung from a dead jelly dried up on the beach, so you should avoid contact without protection.
Stings from a mauve stinger should be treated by a medical professional. The pain can last for up to two weeks and cause a strong red rash and swelling. Occasionally the victim may also suffer vomiting, diarrhea, and dizziness.
The mauve stinger is a bioluminescent jellyfish that can give off flashing light when disturbed, visible to the naked eye at night.
6. Box Jellyfish (Cubozoa)
Several different box jellyfish species, also called sea wasps, are found in Florida’s waters, with most being seen in the Atlantic ocean. Box jellies are amongst the deadliest animals globally, although fortunately, you’ll typically only find the species with the worst stings in Australia.
Just like their name suggests, the translucent bell of the box jelly is square and box-like. Depending on the species, the box can measure up to 30 centimeters / 12 inches in diameter. Box jellies usually have tentacles that can reach as long as three meters / ten feet.
There are also Irukandji jellyfish in Florida which are a tiny species of box jellyfish. These grow from 5 millimeters / 0.2 inches to 25 millimeters / 0.98 inches wide. They have four long tentacles, ranging from only a few centimeters to 1 meter / 3.3 feet in length.
Box jellyfish are strong swimmers and appear to hunt for food actively. Although humans are not on their list of prey, the sting from a box jelly can be highly potent. It will instantly cause excruciating pain, leading to unconsciousness and, in extreme cases, death if untreated.
If you suspect you’ve been stung by a box jelly, you should receive immediate first aid and emergency medical attention.
7. Upside-Down Jellyfish (Cassiopea)
The upside-down jellyfish is an unusual jellyfish often seen in the Florida Keys in well-lit shallow areas of mangrove and seagrass.
This jellyfish takes its name because it spends its time upside-down compared to other species. The branched arms point upward as the upside-down jellyfish rests, pulsing on the bottom.
Upside-down jellyfish release stingers into the water surrounding them to stun their prey and keep away predators, so you might feel a tingling sensation if you swim close to them.
Although they can trap plankton, these jellyfish get most of their food from sunlight which is why they point their arms upwards. Symbiotic photosynthetic algae live in the arms and produce food.
8. Portuguese Man O’ War (Physalia physalis)
Our next entry isn’t a true jellyfish. However, the Portuguese man o’ war looks and acts like one to most people, so it seems reasonable to discuss it here.
The Portuguese man o’ war is a marine hydrozoan found in the Atlantic Ocean and is seen reasonably frequently along the lower east coast of Florida when there are east and southeast winds.
This floating animal has a distinctive gas-filled bladder that’s usually blue, purple, pink, or mauve. Instead of swimming, the man o’ war uses the bladder as a sail to carry it along the surface as the wind blows. It’s also where the common name comes from, as the shape is supposed to resemble a famous fighting ship.
The bladder can rise as high as 15 centimeters / six inches above the water and is usually nine to 30 centimeters / 3.5 to 12 inches wide. Underwater the animal has long tentacles that hang between ten and 30 meters / 30 to 100 feet below. These are used to catch small fish and other prey.
The sting from a Portuguese man o’war is strong enough to be extremely painful. Untreated, the venom can cause breathing and cardiac difficulties, fever, shock, and even death. Immediate medical attention is needed in the event of any sting.
Portuguese man o’ war are often seen beached on the shore, and you should not touch them as the venom remains active even after the animal has died.
9. By-the-Wind Sailor (Velella velella)
The by-the-wind sailor also isn’t a jellyfish. It is closely related to the Portuguese man o’ war and looks like a miniature version of one in many ways.
By-the-wind sailors also drifts along with the wind and ocean currents, and its bright blue sail is very distinctive. Usually, the sail is a maximum of about ten centimeters / four inches high, and the tentacles are extremely small.
Fortunately, the by-the-wind-sailor doesn’t really sting humans. Typical reactions are a mild, itchy rash that quickly clears up.
Florida Jellyfish FAQ’s
What Kind of Jellyfish Are Found in Florida?
There are many different jellyfish species found around Florida. Fortunately, while some can be very dangerous, like the box jellies, the most common types, moon jellyfish and upside-down jellyfish, don’t sting humans.
What Are the Most Common Jellyfish in Florida?
The most common Florida jellyfish is the moon jelly. This round, flat jellyfish is often seen in large numbers in shallow waters. Luckily it only has a very mild sting that most people won’t even feel.
How Do You Identify a Jellyfish?
You can identify a jellyfish by color, shape, and size. It’s important to remember that many jellyfish can still sting even when washed up on the beach and apparently dead, so you should always look but not touch.
What Type of Jellyfish Live In the Gulf of Mexico?
Jellyfish in the Gulf of Mexico include many of the same species as the types of jellyfish in the Florida gulf. You can expect to see common moon jellyfish, mauve stingers, cannonball jellyfish, and occasionally box jelly or a Portuguese man o’ war.
How Should You Treat a Jellyfish Sting?
Thankfully there are plenty of jellyfish that don’t sting in Florida. However, if you receive a jellyfish sting, it’s vital to apply first aid and get medical attention as quickly as possible.
Because different jellyfish stings can require different treatments, you should call your local emergency number (such as 911) to get accurate advice.
General first aid advice from the University of Florida for most jellyfish stings includes:
- Rinsing the jellyfish sting site as quickly as possible with large amounts of household vinegar for at least 30 seconds. Vinegar neutralizes any stingers left on the victim’s skin.
- If you don’t have vinegar available, use ocean water.
- After washing with vinegar, soak the area in hot water 42°C to 45°C / 107°F to 115°F for 20 to 40 minutes.
- Apply antihistamine or cortisone cream.
- Seek medical attention. Monitor patient continually for allergic reaction.
To reduce the chance of getting jellyfish stings, wear a rash guard or stinger suits when swimming, and make sure that you pay attention to purple flag warnings that mean you are more likely to have a dangerous encounter.
Some of the types of jellyfish in Florida can be pretty dangerous, so it’s good to know how to recognize them.
Luckily the jellyfish that appear in large numbers are usually relatively safe. However, it’s always wise to be cautious and stay well away if you are unsure.
British-born Dan has been a scuba instructor and guide in Egypt's Red Sea since 2010.
Dan loves inspiring safe, fun, and environmentally responsible diving and particularly enjoys the opportunity to dive with sharks or investigate local shipwrecks.
When not spending time underwater, Dan can usually be found biking and hiking in Sharm's desert surroundings.