Woman bitten on stomach by blue-ringed octopus

A woman in her 30s has suffered multiple bites from a potentially deadly blue-ringed octopus while cooling down on Sydney's north shore.

Paramedics were called to Chinamans Beach in Mosman around 2.45pm on Thursday.

The woman was swimming when she picked up a shell containing the octopus which fell out and bit her twice on the stomach.

Afterward, she reported abdominal pain around the bite and paramedics applied pressure and a cold compress.

She was taken to Royal North Shore Hospital in a stable condition for monitoring and further treatment.

"A blue-ringed octopus bite is a rare call for us but they are extremely venomous," NSW Ambulance Inspector Christian Holmes said.

Taking their name from the iridescent blue markings they display when threatened, blue-ringed octopuses produce a fast-acting toxin that causes paralysis.

The toxin can be fatal and is known to have caused the deaths of at least two people in Australia and one in Singapore, according to the Australian Institute of Marine Science.

While those that have been bitten remain fully conscious, the toxin paralyses voluntary muscles including the respiratory system, causing some victims to die from a lack of oxygen.

If air is provided manually to a victim of a blue-ringed octopus bite they generally fully recover.

While native to much of the Australian coastline, the marine molluscs, which are small and usually no bigger than 10cm when the arms are extended, are generally shy and retiring and only attack when provoked.

Since the blue rings only appear when the animal feels threatened, victims sometimes mistake them for a more harmless species of octopus.