Scientists in Tasmania have found a new species of unnamed and unclassified sea creature, as its much larger cousin grabs the limelight on the internet.

The new creature is related to a giant gelatinous animal, the pyrosome, that is so elusive it is known as 'the unicorn of the sea'.

The pyrosome can grow up to 30 metres long but it is actually a colony of tiny creatures called zooids, which filter plankton from the water.

Few people have ever seen one, but pictures taken off Tasmania's south-east coast several years ago have re-surfaced on the internet, attracting more than three million views.

"It's not only huge and big enough to scuba dive through but it's a weird, weird creature," said the CSIRO's Dr Lisa-Ann Gershwin.

"It's actually a colony so it's not one big tubular creature.

"It must be like LSD from the 1960s or something to watch these ripples of light going across these colonies in this weird gelatinous flowing tube of light."

The renewed interest in the pyrosome has come just as scientists have discovered its tiny cousin in the same area of waters off Tasmania's south-east coast.

Similar to humans

Dr Gershwin says the as-yet-unnamed creature looks like blobs of jelly in a petrie dish but the animals are surprisingly similar to humans.

"Believe it or not, they're actually more closely related to us than they are to jellyfish," she said.

"They're in our phylum, and in our earliest larval stages and their earliest larval stages, you can't tell us apart."

Both the underwater animals are members of the salp family and could help shed more light on climate change.

"They are also really important in climate change, believe it or not," Dr Gershwin said. "The lowly salp is important to us because they sequester carbon into the deep sea."

Scientists hope to name the new creature by the end of the year.

"We haven't picked a name for it yet, so we're open to names, if you have any ideas," Dr Gershwin said.

Scientists will return to the water in October, hoping the large seasonal swells off Tasmania's coast will dredge up more mysterious creatures lurking in the depths.