Biologist at Macquarie University Professor Culum Brown said the peculiar fish was larvae from a species of eel that “hatch way out in the ocean and are initially part of the plankton”.

“They are small, thin, flat and transparent and as they approach the coast they gradually change and start to become more elongate — the typical eel shape — and become green/brown in colour,” he said via Yahoo News.

“Soon after they start to migrate up rivers and creeks and become increasingly like baby eels (ie they look like little adult eels).”