A crew member on a tourist boat has been stung by a cone snail on Whitsunday Island off north Queensland, causing his respiratory system to start shutting down.

The 25-year-old was walking barefoot in shallow water near Whitehaven Beach when the cone snail's harpoon pierced his skin about midday on Tuesday.

Considering the incoming tide, there was only a small window for the man to be flown to hospital, RACQ CQ Rescue crewman Ethan Clissold said.

The pilot managed to land on a narrow patch of sand at Tongue Bay and the patient was brought to the helicopter by an inflatable boat.

"If we had any delays in getting him on the helicopter so the medical team could stabilise and administer pain relief, we would have needed to rethink our landing strategy, wasting precious time in the process," Mr Clissold said.

The man was taken to the Mackay Base Hospital where he remains in a stable condition.

What is a cone snail? A cone snail has a cone-shaped shell, a head and tentacles

A cone snail has a cone-shaped shell, a head and tentacles They are typically found in warm tropical seas

They are typically found in warm tropical seas There are over 800 different species

There are over 800 different species Cone snails are carnivorous and predatory, using a venomous "harpoon" to sting prey

Cone snails are carnivorous and predatory, using a venomous "harpoon" to sting prey Different venom can paralyse fish and even kill humans

Different venom can paralyse fish and even kill humans They eat marine worms, small fish and even other cone snails

Aside from the pain, cone snail's venom can, in severe cases, cause muscle paralysis, vision impairment, respiratory failure, and can be fatal.

Few know its full effect with just 36 people dying from the unassuming killer in the past 90 years, University of Queensland chemistry professor David Craik said.

The cone snail has a proboscis that hangs out like a lure to attract fish, which are then harpooned.

At the end of the proboscis they have a hollow tooth, through which the venom is injected.

The venom is designed to paralyse, however not much is needed for it to kill fish, or humans.

In the case of the tour crew member, Dr Craik said the venom would have blocked his nerve impulses that control muscles associated with breathing.

"The fatal dose of the venom could be as little as two milligrams for a 70 kilogram adult so that's comparable sort of toxicity to what you get with some snakes," he said.

"It is a pretty deadly venom and if you're unlucky enough to have a decent amount injected then potentially the consequences could be fatal."