Taxonomy [Medusozoa] [Phylum: Cnidaria] [Class: Scyphozoa] [Family: Ulmaridae]
Jellyfishes are soft-bodied free-swimming invertebrates.
The lack of any bones or a protective shell means their marine environment supports their jelly-like symmetrical delicate body.
Most species have round or oval umbrella-shaped upper bodies called the bell and their mouth is located below near to the trailing tentacles.
In fact, the species known collectively as a 'Fluther of Jellyfishes', surprisingly belong to the same Cnidaria animal classification as sea anemones and corals.
Jellies are carnivorous. They feed most on other invertebrates and zooplankton.
In simple terms, they kill their prey using specialized stinging venomous cells within the tentacles. After their victim has been immobilized with the poison the meal is directed into its mouth by its oral arms.
Jellyfish exist in marine environments and saltwater lakes. Some of the estimated 900 different species of jellyfish live in warm tropical open oceans zones whereas others prefer cold water arctic locations.
They thrive in shallow inshore waters as successfully as deep dark underwater terrain. Freshwater jellyfish are Hydrozoans.
Scuba diving around jellyfish is increases the risk of being stung. Nonetheless, if you use caution and stay some distance away, they are fascinating and enchanting ocean marine creatures to watch.
Jellyfish encounters are incredibly photogenic as they pulsate and sluggishly drift along with ocean currents.
A Jellyfish has a soft gelatinous body which is usually a transparent sac and dangling tentacles. They may appear non-threatening, harmlessly drifting with tidal currents, however, exactly how dangerous are jellyfish stings?
Their bodies might appear unprotected, but despite their perceived vulnerability the majority totally avoid being eaten by their predators and survive to reach full maturity. They protect themselves from harmful attacks by their tentacles.
Jellyfish tentacles can grow more than one meter in length and their transparency makes them almost impossible to identify underwater. Each tentacle contains a seemingly uncountable number of nematocysts.
Nematocysts are stinging cells used to stun jellyfish prey. If you get stung, they cause excruciating pain, swellings, and severe irritation. The most dangerous jellyfish species have developed stinging cells so powerful that they can seriously harm or cause death to humans.
Despite the potential danger, getting stung by jellyfish while scuba diving is relatively uncommon and rarely considered a major threat.
Jellyfish broadly drift in the upper levels of water close to the surface and the sting is harmful only if it makes physical contact with bare skin. Therefore, jellies are more likely to sting swimmers and beach paddlers than scuba divers.
Divers usually wear a protective wet suit and gloves which leaves little exposed skin. Despite this protection, you should always stay well clear of jellyfish if you spot them in the water.
Dive centers and experienced dive guides will be cautious of any dangerous jellyfish in the water and will alert visiting divers to any seasonal invasion or local sightings.
Jellyfish stings are dangerous for several potentially fatal reasons. Although some people tolerate mild stings better than others, some people suffer extreme reactions to a sting.
The sting is effectively a dosage of potentially life-threatening venom or poison. The toxicity is related to the species and affects people with differing symptoms and outcome.
The body’s reaction to a sting is also related to the person’s size and chemistry. Generally, smaller people will suffer more severe reactions with greater effects which may result in anaphylactic shock.
The Box Jellyfish (Chironex Fleckeri) is the most toxic species which is found in Australia and parts of Indo-Pacific regions. A sting from this deadly jellyfish species is known to kill a human in less than 5 minutes.
Jellyfish stings should be treated immediately. Medical research centers and dive safety organizations both recommend using vinegar as the most successful initial treatment for a sting. Divers should use vinegar because it neutralizes the stinging nematocyst cells.
Applying liberal amounts of vinegar helps to reduce pain and minimize discomfort from the irritation. It also helps to slow or stop the venom from spreading around the body. This immediate treatment is particularly important and potentially life-saving if the sting is by one of the most toxic species such as the Box Jellyfish.
Dive boats usually have vinegar on board or in the first aid kit. If you do not have vinegar available you may use salt water as a rinsing agent. Baking soda is also capable of neutralizing sting cells.
Despite being in many a ‘divers' tale’, urinating on someone's jellyfish stings is not an official recommendation by medical professionals. Doctors also suggest that rinsing stings with freshwater may cause the nematocysts to fire and therefore should not be used.
Jellyfish tentacles are extremely sticky. They adhere to the bare skin and they should be removed after you have neutralized the stinging cells. Use a razor to shave the affected area or scrape the tentacles free with a clean credit card or something similar.
You can also use tweezers to remove individual jellyfish tentacles. Remember to wear thick gloves to protect your own hands.
When recommended first aid supplies are not available, use hot packs or dry cold packs to reduce pain and sand may be used as an abrasive to scour the jellyfish sting area.
Apply hydro-cortisone cream if available and monitor the victim's breathing and reaction to the sting. In most incidents you should seek medical advice as soon as possible because the victim may require a shot of epinephrine or antivenin treatment.