On their own, the neon-blue patches lighting up the night waters of the River Derwent in Tasmania would usually be a show stopper.

But mother nature has put on a rare double, with a light show taking place in the water complemented by the Aurora Australis which has splashed light and colour across Hobart's skies.

"It's pretty impressive," said amateur photographer Wayne Painter.

The deep sulphur-coloured glow in the water is called bioluminescence, which is caused by a micro-organism called Noctiluca scintillans​. A chemical reaction inside the organism gives off the light when disturbed by movement, making the water appear blue.