For rock fishermen, sea squirts such as cunjevoi provide a readily available source of flesh for bait.
For children on beach holidays, they provide hours of fun. Stepping on them so they spurt out water is a summer ritual.
Now these creatures that grow on rocky foreshores have also provided important clues about how our backbone, brain, heart and other bodily systems evolved.
An international team of researchers has deciphered the genetic code of the sea squirt and found that about 80 per cent of its genes are present in humans and other vertebrates.
Team member Dr Bernie Degnan, of the University of Queensland, says the DNA analysis suggests that one reason we are a lot more complex than these rock dwellers is because we have duplicate versions of many of these genes. "We may have three or four copies of a gene and it has one."
Genetically, a sea squirt is like a "stripped-back vertebrate", he says, which makes it ideal for studying the evolution of more advanced creatures.
Although they are squashy in their adult form, sea squirts in their tadpole-like larval stage have a primitive backbone and nervous system.
The genetic study of Ciona intestinalis, a less leathery species than cunje, was published earlier this month in the journal Science.
It has proved Charles Darwin right when he first suggested in his 1871 book The Descent of Man that sea squirts, or ascidians, and vertebrates had diverged from a common ancestor that existed about 550 million years ago.
Mike Levine, professor of genetics at the University of California, Berkeley, says the new DNA analysis is "entirely consistent" with Darwin's description of one branch "retrograding in development and producing the present class of Ascidians, the other rising to the crown and summit of the animal kingdom by giving birth to the Vertebrata".
Although the two branchs of life began with the same raw genetic material, the new study suggests that duplication of genes had taken place early in the evolution of vertebrates.
These redundant copies had then evolved to perform other functions that allowed vertebrates to become more complex creatures than sea squirts, developing sophisticated immune, nervous and hormone systems, the research team said.
It found squirts have about 16,000 genes, half the number in humans. They have light-sensing genes similar to those in vertebrates and genes involved in forming the heart and thyroid. But they lack the hundreds of genes that are the key to our immune systems.