Marine stinger beach sign
                                                              ©Johan Larson

Australia’s coastline of 35,000 kms boasts over 10,000 beaches, which is more than any other country in the world. And with more than 85 percent of our population living 50 kilometres or so from the coast, leisure time at the beach and participating in water activities are a vital part of the laid-back Australian lifestyle, however a dip in the ocean or waterways can also take you right into the habitat of some of our more venomous marine creatures.

The ones that can pose a risk to humans if encountered during beach or ocean activities are:

  • Venomous jellyfish - Box jellyfish & Irukandji jellyfish
  • Blue-ringed octopus
  • Stonefish
  • Sea snakes
  • Stingrays

VENOMOUS JELLYFISH – Marine stingers:

BOX JELLYFISH – have a transparent pale blue, box-like shape up to 20x30cms, with tentacles around 3 metres in length. Each tentacle has approximately 5,000 stinging cells or nematocysts which release venom that causes extreme pain on contact; it is considered the most poisonous in the world. Box jellyfish are almost invisible in the ocean and will gather in calm but murky inshore waters and near creek/river mouths to feed following heavy rainfall.

Symptoms: The toxins affect the nervous system, causing cardiac arrest, paralysis and death within a few minutes of envenomation. The more tentacles that come into contact with the skin, the more venom is released and, due to their length, there have been cases of rescuers also being stung. Survivors can continue to suffer debilitating pain for weeks with significant scarring of the skin.

IRUKANDJI JELLYFISH - are both the smallest and one of the most venomous jellyfish in the world. An adult grows to approximately 1-2cm square, with 4 translucent tentacles each up to a metre in length. Nematocysts are located on the bell as well as the tentacles.

Symptoms: A sting from 2 of the Irukandji species (Carukia barnesi and Malo kingi) results in symptoms often known as ‘Irukandji syndrome’, that can be life threatening. Symptoms can take up to 40 minutes to manifest and may include headache, lower back pain, muscular cramps, chest pain, abdomen pain, nausea, vomiting and breathing difficulties leading to respiratory failure. They have also been known to cause fatal brain haemorrhaging.

Where are they found?

Both jellyfish species are found along the northern coastline from Broome in Western Australia, across the north coast of the country and down the east coast of Queensland as far as Bundaberg and Fraser island. While box jellyfish are more commonly found in coastal waters, Irukandji are solitary creatures of the open waters that are swept towards the coast by summer winds and currents. They have (rarely) been found further south.

Risk to travellers:

The jellyfish are present in our seas all year round but the risk is higher during peak season, which in the Top End coincides with the wet season from around October/ November until May. The season is usually a little shorter further south.  

Marine stingers prevention:

  • Swim on patrolled beaches between the red and yellow flags
  • Pay heed to Marine stinger signs
  • Marine activities should be done with a buddy
  • Don't touch marine stingers washed up on the beach, they can still sting you
  • Consider swimming in full-body lycra swim suits to protect against marine stings

Marine stingers management:

Call 000 - Emergency first-aid is imperative and cardiopulmonary resuscitation may be required. 

  • Remove the victim from the water.
  • Immediately saturate the area with vinegar - avoid rubbing the sting site.
  • If vinegar is not available, carefully remove pieces of tentacles and non-discharged nematocysts and rinse well with seawater.

NOTE: Many other jellyfish can cause very painful stings but they are not life-threatening. The most common is the Bluebottle jellyfish (or Pacific man-o-war) which is translucent blue (2-15cm body lengths), has one tentacle up to 10 metres long and can be found all along the coastline of Australia. Vinegar should not be used with Bluebottle stings. The advice is to wash off any tentacles with seawater and don’t rub the affected area. Heat will neutralise the venom, so if possible, immerse the sting site in water that is as hot as can be comfortably tolerated (there is evidence that 40 degrees for 10 minutes provides relief from the pain). For extensive sting areas, or if they are on the face and neck, or if symptoms persist, contact emergency services for an ambulance.

(For more information, a Tasmania-based marine biologist specialising in jellyfish, Dr Dr Lisa-ann Gershwin, has developed the Jellyfish app ($) in which she provides ‘instant access to a wealth of useful information about jellyfish around the world’, with sections that include Jellyfish Near Me, Species Info, FAQs and Current Alerts.)


The blue-ringed octopus is one of the world’s most venomous creatures. They are small (4-6 cms and 8 arms reaching to 10 cm) and sandy-coloured, with bright iridescent blue rings that appear on their bodies when they feel threatened and are about to attack. Their powerful toxin easily kills their prey of crabs and small fish, but the chemical it contains (tetrodotoxin) acts rapidly to paralyse the voluntary muscles in humans and consciousness is not affected even though the victim cannot respond. Death results from lack of oxygen through paralysis of the breathing muscles if immediate resuscitation is not commenced. Small children are more at risk from the bites of these non-aggressive molluscs and fatalities have been recorded, usually when the creatures are handled.

Where are they found?

These octopuses are only found in the temperate waters of southern Australia, from southern Western Australia along the coastline to eastern Victoria. They hide under rocks and in crevices in intertidal areas during the day and move about at night.

Risk of Blue-ringed octopus envenomation:

Blue-ringed octopus bites are very rare but extremely dangerous. Only two deaths have been recorded in Australia, but many people have come close to death after being bitten.

Prevention - Blue Ringed Octopus bite:

  • Be aware if in a risk area
  • Wear shoes/sandals when exploring rock pools
  • Do not prod or poke any marine life or into any crevices in rock pools

Envenomation Symptoms:

Blue-ringed octopus bite may be painless or similar in intensity to a bee sting. Some cases may not become symptomatic for up to 40 minutes after being bitten.

  • Early onset: difficulty swallowing, excessive saliva, tingling, numbness of lips and tongue, light headed, headache, loss of vision and nausea.
  • Escalating symptoms: chest tightness, paralysis, respiratory failure, hypoxia, death

Bite management:

  • Immediately call 000 for emergency medical care
  • Monitor breathing and airway.
  • Apply mouth-to-mouth resuscitation if necessary
  • Wash sting area with fresh water
  • Apply pressure immobilisation bandage and splint the limb


Stonefish are the most venomous of all fish. Two species are present in Australia: the Estuarine and Reef stonefish are approximately 30 cms in length, brown and grey in colour, and they are well-camouflaged, looking like encrusted rocks or pieces of coral. Each species’ dorsal fin is lined with 13 spines that the fish erects as a defensive tactic when threatened. When pressure is applied, ie when the fish is stepped on, the spines act as hypodermic needles, injecting a potent venom that acts on the cardiovascular and neuromuscular systems. The fish is able to survive out of water for up to 24 hours.

Where are they found?

Stonefish can be found throughout the shallow coastal waters in the northern half of Australia. They live amongst the rocks on coral reefs, in rock pools, amongst aquatic plants, mud or sand and emerge at night. Estuarine stonefish may partly buried in the sand of shallow waters during the day.


Immediate and excruciating pain that may be followed by muscular paralysis, respiratory difficulties, cardiac failure and death.

Sting prevention:  

Wear sturdy, thick-soled shoes when walking or wading in shallow water along the coastline. Don’t disturb or pick up rocks on the reefs on any that are washed onto the beach.

Envenomation management:

Call 000 - Emergency first-aid is imperative and cardiopulmonary resuscitation may be required. 

  • An antivenom has been in use since the late 1950s for stonefish envenomation.
  • Wash the wound immediately with seawater or cold water
  • If available, soak the area in water that is hot enough to be tolerable but not to burn until emergency help arrives.


There are approximately 32 sea snake species in Australia which are found in all regions, including off the Tasmanian coast and even along inland waterways over 100kms from the ocean. They are all venomous, however are less likely to be aggressive and usually do not bite. (Most bites are reporting on fishing vessels when the snakes are hauled on board with the catch.) Early symptoms of local pain and muscle spasms may precede the development of ‘blurred vision, drowsiness and respiratory paralysis’.  An antivenom is available.


Stingrays are curious, playful animals and they are not aggressive, however a stingray’s spine has serrated edges and a sharp point that may release venom. They camouflage themselves under the sand, so can be easy to step on. If threatened their instinct is to swim away but they may also whip their tail in defence. It is very rare to die from a stingray injury, but it is possible by going into shock and cardiac arrest if stung in the chest or abdomen.

Stingray injury treatment:

  • Flush the wound with fresh water 
  • If available, soak the wound in hot water
  • Use tweezers to remove the stingers
  • Scrub the wound with soap and fresh water.
  • Apply pressure to stop bleeding.
  • Call emergency services and commence CPR if shock/cardiac symptoms occur