Bluebottles have been found all down Tasmania's east coast, along the New South Wales' coast, in parts of Victoria and even South Australia. 

Biologist and jellyfish expert Dr Lisa-ann Gershwin said the bluebottles were at the mercy of the wind.

"At the moment we are seeing what can only be described as, scientifically of course, a gobsmacking abundance of these things," Dr Gershwin told ABC Radio Hobart.

"We have a massive armada of bluebottles all along Tassie's east coast right now."

Dr Gershwin said it was normal for sustained north-easterly winds to bring the bluebottles to shore, and Cyclone Seth could have contributed.

"But we are seeing a lot, even before Seth came in," she said.

While the sight of bluebottles is distressing for swimmers, Dr Gershwin described them as "very beautiful and interesting".

A bluebottle 'Armada':

Dr Gershwin said bluebottle populations were larger in summer because they bred more in warmer months, but wind was the key factor.

"It's not just a summertime thing; it has to do with sustained onshore winds," she said.

"When a wind comes up it drives these armadas to shore.

"That just means we see them more this time of year, but we can see them anytime."

An 'Armada' is the collective noun for bluebottles — aptly named because Dr Gershwin said they were usually floating out in the open ocean in huge numbers.

The bluebottle has a blue bubble or bladder, and a single fishing tentacle.

A bluebottle is different to a true jellyfish and is made up of a complicated colony of four individuals with both male and female parts.

"Each bluebottle colony are either left-handed or right-handed in terms of their sail," Dr Gerswhin said.

"Whether they are left-handed or right-handed determines which ones get picked up by any given wind.

"It's nature's way of making sure it doesn't kill off the entire population at once."

The bluebottle is closely related to the larger Portuguese man o' war, which is found in the Atlantic.

The species found in Australia is the Pacific man o' war.

How to treat a sting — use sea water first

While the most common species of bluebottle found on Australian beaches is not life-threatening, the sting is painful.

Dr Gershwin said microscopic stinging cells inject venom into the skin.

"It hurts like hell," she said.

"Most people want to go straight for something that is going to take care of the pain, so for that we use hot water or ice.

"But most people don't consider that fresh water forces an immediate massive discharge of all of the stinging cells that haven't fired yet.

"So you can take on many times more venom simply by going for the fresh water first."

She said it was important to use sea water first to wipe away the stinging cells before they discharge more venom.

Bluebottles can still sting even when washed ashore, and Dr Gershwin said it was best not to touch them at all.

"When they are good and dead they can still sting as soon as they rehydrate," she said.

Story By | Georgie Burgess