Box jellyfish, scientifically classified under the class Cubozoa, are known for their distinct, cube-shaped bell and potent venom. Box jellyfish are present in Florida waters, but they are not the species responsible for the high fatality rates seen in the Indo-Pacific region. While the presence of any box jellyfish warrants caution, the species found locally present a significantly lower risk level to swimmers.
Confirming Presence and Species in Florida Waters
Florida’s coastal environment is home to at least two documented species of box jellyfish, neither of which approaches the danger level of the Australian box jelly, Chironex fleckeri. The most common species is the Four-handed Box Jelly (Chiropsalmus quadrumanus), found along both the Atlantic and Gulf coasts of Florida. This species is generally more widespread and poses the greater threat of the two local varieties due to its size and longer tentacles.
A smaller species, the Mangrove Box Jelly (Tripedalia cystophora), has also become established in the southern regions, often near Boca Raton and the Florida Keys. This diminutive creature typically lives among the prop roots of red mangrove trees, specializing in feeding on copepods. The T. cystophora is very small, often less than one centimeter across its bell, and is not known to cause serious harm to swimmers.
Box jellyfish are found year-round in the tropical and subtropical waters surrounding Florida, with their presence in nearshore areas often increasing during warmer months. Unlike the Australian species, which can cause cardiac arrest within minutes, the Florida varieties primarily result in painful, localized stings.
How to Identify Florida’s Box Jellyfish
The defining characteristic of the class Cubozoa is the distinct, box-like or cube-shaped bell, which gives them their common name. This bell is typically transparent or pale, making the animal difficult to spot while suspended in the water. The box jellyfish features four flat sides when viewed from above.
The tentacles originate from four distinct corners of the bell, which is a key visual identifier. The Four-handed Box Jelly (Chiropsalmus quadrumanus) can grow to approximately five inches in bell length, with tentacles that may extend up to 10 feet. Conversely, the Mangrove Box Jelly is much smaller, with a bell only about a quarter of an inch in diameter.
Box jellyfish are also unique because they possess 24 eyes clustered on the bell, allowing them to actively hunt rather than simply drifting with the current. This ability to swim with speed and directional control sets them apart from common local species, such as the Moon Jelly or the Portuguese Man O’ War. The Portuguese Man O’ War is often mistaken for a box jelly, but it is actually a siphonophore, a colony of specialized organisms.
Immediate Action for Stings
A box jellyfish sting requires immediate and specific first aid to prevent further envenomation from unfired stinging cells, or nematocysts. The first step is to exit the water immediately and rinse the affected area thoroughly with saltwater. Never use fresh water, as this can cause any remaining stinging cells to discharge more venom into the skin.
The next step is to liberally apply white vinegar (acetic acid) to the sting site for at least 30 seconds. Vinegar neutralizes unfired nematocysts, effectively preventing them from releasing their toxic contents. After the vinegar application, any visible tentacles should be carefully removed using tweezers or a gloved hand.
For managing the intense pain, soaking the affected area in hot water, with a temperature between 104 and 113 degrees Fahrenheit, is recommended. The heat helps to denature the venom proteins and can provide significant relief from the burning sensation. If severe symptoms develop, such as difficulty breathing, chest pain, an allergic reaction, or if the sting covers a large portion of the body, immediate emergency medical attention is necessary.