Platypus (Ornithorhynchus anatinus)
In Australia, it's not only the scary animals that are venomous. That would be too easy. The platypus looks something like a cross between a fluffy duck and a beaver, but not many people realise it's also one of the few venomous mammals. Male platypuses (yes, that's the proper plural form of the name) have a spur on their hind foot that delivers excruciating venom that can incapacitate humans and kill dogs and cats. And while it might not be deadly to us, anecdotal evidence suggests the pain develops into long-lasting hyperalgesia (a heightened sensitivity to pain) that lasts for weeks.
Scientists believe these venomous spurs have a unique evolutionary purpose - rather than killing and incapacitating prey, they're used to assert dominance over other males during the breeding period. Brutal.
Blue-ringed octopus (Genus Hapalochlaena)
With blue rings that glow and pulsate when the octopus is angry, this cephalopod is undoubtedly beautiful to look at. But it's also one of the only reef inhabitants that has a bite that's deadly to humans but has no known anti venom. The octopus only grows between 12-20 cm, but can reportedly deliver enough poison to kill 26 humans. They live off most of Australia's coastlines in tidal pools and coral reefs and eat small crabs and shrimp - after piercing their prey's exoskeleton with their horny beak they release their paralysing venom and suck out its flesh.
The good news is there have only been three known human deaths attributed to blue-ringed octopuses in Australia and hospital admissions are extremely uncommon.
Red lionfish (Pterois volitans)
Look at those stripes and elegantly fanned spines - who wouldn't want to run into the red lionfish while snorkelling? You, if you're smart. The spines of the red lionfish happen to carry an extremely painful venom. While it's not known to be fatal to humans, it can cause pain, headaches, vomiting and breathing difficulties. The fish are found all over the Indo-Pacific region, and in oceans off the coast of east and western Australia.
Cone shells (Conus sp.)
How much damage can a shell do, you might ask. Quite a lot, if it's the innocent-looking cone shell, which lies on the bottom of the ocean and shoots its harpoon-shaped proboscis at fish that swim too close, striking them with venom 1000 times stronger than morphine.
There are a range of different cone shell species, but generally their barbs can pierce through wetsuits and gloves and the venom can affect human muscles and nervous system, causing death. The venom is so effective it's actually being used in a drug called Ziconotide to relieve chronic pain. A single sting from one of these molluscs could reportedly kill 15 healthy adults, but only one death has been recorded in Australia in 1935.
Pfeffer’s Flamboyant Cuttlefish (Metasepia pfefferi)
Living off the waters of northern Australia is this beautiful and unique cuttlefish, which can change its vibrant colours and patterns rapidly and actually "walks" along the bottom of the sea. The appropriately named Pfeffer's flamboyant cuttlefish is also special because it produces an extremely deadly toxin in its muscle tissue, making it the only known poisonous cuttlefish at this time. The good news is that scientists have found so far that the cuttlefish can only kill you if you eat it (and we know that makes it poisonous rather than venomous, but we thought it was cute and deadly enough to be included on this list).