How to Identify Dangerous Marine Animals in Australian Waters

Australian coastlines and beaches are beautiful places to relax and enjoy the water. However, these locations are home to some dangerous marine animals which must be respected and avoided to keep everyone safe. Learn the warning signs of creatures like blue-ringed octopuses, box jellyfish, and crocodiles, and always take safety precautions like swimming in safe zones and obeying warning signs. Once you know what you’re looking for, relax and enjoy a fun day out!

Method 1

Method 1 of 4:

Spotting Molluscs and Jellyfish

1
Expect blue-ringed octopuses in shallow reefs and coral rock pools. Blue-ringed octopuses are found across most Australian coastlines and they spend most of their time hiding. Look for small, 12–20 cm (4.7–7.9 in) brown octopuses around rocks and shells, and leave the water immediately if you spot one.^{[1]XResearch source}
- When these creatures feel threatened, they develop bright blue lines and rings, making them much easier to spot.
- Blue-ringed octopuses aren’t aggressive and are actually quite shy, but they will bite if touched.
- Most blue-ringed octopus bites are accidental, as it’s easy to touch or stand on one without noticing.
2
Watch out for box jellyfish and Irukandji at tropical beaches. Box jellyfish have a bell (body) that looks like a box with 4 corners. Each corner has up to 15, 3 m (9.8 ft) long tentacles. Irukandji are only the size of a fingernail, yet have tentacles that can each extend up to 1 m (3.3 ft) long.^{[2]XResearch source}
- Beaches in Queensland, Northern Territory, and Western Australia are home to box jellyfish and Irukandji. Rely on signals like washed up jellyfish, clouds of small prawns, and calm weather with a northerly breeze, as it can be difficult to spot these types of jellyfish in the water.^{[3]XResearch source}
- Irukandji syndrome develops within minutes of a sting and the symptoms include back pain, nausea, and difficulty breathing. Seek emergency medical treatment and pour vinegar over the site if possible.^{[4]XResearch source}
3
Check the beach for washed up jellyfish to spot bluebottles. Bluebottle jellyfish are 2–15 cm (0.79–5.91 in) long and look like thin, blue bubbles. They relatively easy to spot in clear water and the tide is often littered with bluebottle bodies if these small jellyfish are close by in the sea.^{[5]XResearch source}
- Don’t touch washed up jellyfish, as they can still sting.^{[6]XResearch source}
4
Avoid touching any shells to prevent a cone shell attack. Although cone shells look like innocent, pretty shells, they are actually predatory sea snails which have teeth similar to a harpoon. These sea snails are approximately 12 cm (4.7 in) long and they have a bright shell pattern in brown and cream.^{[7]XResearch source}
- When a cone shell is disturbed, the tooth injects a potentially deadly venom into the victim.^{[8]XResearch source}
- Cone shells are found under sand, stones, and weeds throughout Western Australia, Northern Territory, and Queensland.
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Method 2

Method 2 of 4:

Identifying Fish and Corals

1
Expect stonefish in shallow, coastal waters. Stonefish are greyish brown, have warty skin, and are 28–42 cm (11–17 in) long. They are very venomous yet are difficult to spot, as they camouflage perfectly around sand and rocks. Stonefish have 13 sharp spines and each of these contains venomous glands that can injure unsuspecting swimmers, waders, and fishers.^{[9]XResearch source}
- Stonefish are common in Queensland, Northern Territory, and Western Australia.
- Stonefish spines are strong enough to pierce rubber-soled shoes.^{[10]XResearch source}
2
Beware of stingrays in shallow, murky water during rising tides. They have large, flattened bodies and a tail with barbed, stinging spines. A stingray only tends to sting if you accidentally stand it, so it’s best to only wade and swim where you can see the ground clearly.^{[11]XResearch source}
- Stingrays are common throughout most coastal areas of Australia.
- Stingrays are often in rising tides as this is where they feed on worms, small fish, and crabs.
3
Look out for sharks in murky water and estuary outlets. Although shark bites are rare, it’s important to be cautious as an attack can be fatal. The 3 dangerous shark species in Australia are Bull Sharks, Tiger Sharks, and White Sharks. Bull Sharks are approximately 2.4 m (7.9 ft) long, while Tiger and White Sharks are 3–4.3 m (9.8–14.1 ft) long. All of these shark species have a whiteish-grey coloring.^{[12]XResearch source}
- Sharks are found in the coastlines, rivers, and estuaries of all Australian states, but are the most common in Queensland, Western Australia, and Southern Australia. Avoid places where there are schools of fish and murky water, as these are preferred shark spots.^{[13]XResearch source}
4
Watch for fire corals when exploring coral reefs. Fire corals have yellow, green, or brown skeletons and are approximately 24 cm (0.79 ft) tall. There are tiny pores in the skeleton from which tentacles protrude and sting.^{[14]XResearch source}
- Although fire corals are quite rare and it’s unlikely that you will come across one, it’s best to avoid touching any form of coral or plant-like animal to be on the safe side.
- Despite the name, fire corals aren’t actually true corals. Instead, they are more closely related to jellyfish.^{[15]XResearch source}
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Method 3

Method 3 of 4:

Recognizing Reptiles and Sea Urchins

1
Anticipate crocodiles in shallow fresh and saltwater. Crocodiles are protected animals in Australia and they are approximately 5.2 m (17 ft) long. They have huge, powerful jaws and thick, strong tails.^{[16]XTrustworthy SourceNational GeographicWebsite of the National Geographic SocietyGo to source}
- Crocodiles commonly live in Northern Queensland, Northern Territory, and Western Australia.^{[17]XResearch source}
- Avoid rivers, estuaries, and coastlines where the water is murky and there are crocodile warning signs. Drag marks and flattened vegetation at the water’s edge are also good indicators of crocodiles.
- When you are in a crocodile habitat, it’s safest to never enter the water or be close to the water’s edge.^{[18]XResearch source}
2
Look out for sea snakes in Northern Australia. All 31 sea snake species in Australia are venomous, however, most are docile and tend to flee from people. The two most venomous species in Australia are the yellow-bellied sea snake and the beaked sea snake.^{[19]XResearch source}
- Yellow-bellied sea snakes have yellow and black bodies and are around 1 m (3.3 ft) long, while beaked sea snakes are grey with white bands and are up to 1.4 m (4.6 ft) long.
- Sea snakes tend to live in tropical, warm waters, such as those in Queensland, Northern Territory, and Western Australia.
3
Be wary of sea urchins in rock pools and coral reefs. Sea urchins can be a variety of colors, including red, brown, cream, and purple, and are 10–20 cm (3.9–7.9 in) in length. These small creatures live on the seabed and are covered with mobile spines. Not all sea urchins are venomous, but the spines can still cause injuries and can be difficult to remove.^{[20]XResearch source}
- Sea urchins are found throughout Australian waters.
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Method 4

Method 4 of 4:

Enjoying the Water Safely

1
Call 000 for emergency medical treatment if you have concerning symptoms. Check for symptoms such as difficulty breathing, trouble moving, numbness, a large loss of blood, chest pain, or nausea. If any of these symptoms are present, contact emergency services immediately. Alert the lifeguard if you are at a beach, as they will be able to give some advice and treatment while you are waiting for emergency services.^{[21]XResearch source}
- Always seek emergency medical treatment for any injuries caused by blue-ringed octopuses, box jellyfish, Irukandji, cone shells, stonefish, stingrays, sharks, crocodiles, and sea snakes.
- Injuries from fire corals, blue bottles, and some sea urchins may not require emergency treatment but do still need medical attention. Use your own best judgment and always call emergency services if you are unsure.
- Although box jellyfish and Irukandji stings require emergency medical treatment, in the meantime pour vinegar over the site if possible. This helps to reduce the pain.^{[22]XResearch source}
2
Obey all warning signs about marine animals. Locations will often have warning signs if any dangerous marine animals are frequently in the area. Always read the signs carefully before you enter the area and follow all of the instructions to keep yourself safe. Obeying the warning signs and being cautious is necessary regardless of if you are swimming, wading, fishing, surfing, or simply being around the water.^{[23]XResearch source}
- Warning signs are common in areas with sharks, crocodiles, and jellyfish.
- Don’t assume that no warning sign means that it’s safe to enter the water. Always use your own best judgment and ask a local for advice if you are unsure.
3
Swim only in designated safe zones. Due to the variety of dangerous marine animals in Australia, there are often designated safe swimming zones at most popular beaches. Always swim between the flags at these beaches, as this is the area that has been checked and cleared as safe. Follow all instructions from the lifeguard.^{[24]XResearch source}
- Swimming only in safe zones is also the best way to avoid rips and dangerous tides.
- Safe swimming zones can change throughout the day as the water changes.
4
Wear a full body wetsuit whenever possible. Full body wetsuits provide great protection against jellyfish stings. Look for a wetsuit that covers 75% to 80% of your body for the best protection.^{[25]XResearch source}
- Full body wetsuits also have the added bonus of preventing sunburn!
5
Stay only in clear water and during the day. It’s safest to swim, fish, surf, and wade in clear water because you can see your surroundings and are less likely to accidentally touch or stand on animals. Stick to being in or around water only in full daylight and avoid the water between dusk and dawn, as the visibility is too low to spot any danger signs.^{[26]XResearch source}
- Always avoid murky water as visibility is low and this is where sharks prefer to live.
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Tips

Don’t let a fear of dangerous marine animals put you off enjoying the water! Simply use your own common sense, obey the rules, and check for any warning signs first.
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Warnings

Never leave young children unattended in or around the water, as their curiosity can attract them to potentially dangerous animals. Teach kids early on about warning signs and what to do in an emergency.
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