This "alien-looking" creature found washed up on a popular beach poses a highly dangerous threat to dogs.
Visitors at Leighton Beach in Fremantle, Australia, were baffled by the huge beast on Monday.
One man shared a photo of it on Facebook.
"ID on this alien looking thing that washed on Leighton Beach," he wrote.
Other Facebook users struggled to identify the creature.
But today, one person posted: "Don't touch it - that’s a dog killer."
And it has since emerged the animal is most likely a sea hare, which indeed has purple ink poisonous to dogs.
Sea hares produce the liquid when they're alarmed. It is used therefore as a defence mechanism.
Professor Culum Brown, from the Department of Biological Sciences at Macquarie University in Sydney, told Yahoo News: “They are mildly toxic, depending on the algae they have been eating."
Speaking previously, Dr Joshua Ovens, Swans Veterinary Services associate vet, told anyone who believes their dog may have eaten a sea hare to contact a vet immediately.
"In terms of clinical signs, if your dog has licked or eaten one, they’ll tend to drool excessively, they can get muscle spasms and begin shaking, vomiting and it can progress to seizures and possible death if they get a really large dosage,” he said.
There are 23 known species of sea hares in the Indo-Pacific Ocean.
Fully grown adults can weigh up to 14kg.
