Lucky witnesses to a spectacular natural night-time show illuminating Port Phillip Bay can thank microscopic algae for the bright flashes and glowing clouds of blue.

While it may appear something out of science-fiction, the dazzling blue light is being created by the presence of noctiluca, a non-toxic form of bioluminescent dinoflagellate that lights up when agitated by night and causes a blooming 'red tide' by day.

Bioluminescence in Port Phillip Bay, end of North Road. Credit:Andrew Watkins

The light shows have been reported at bayside locations including St Kilda, Elwood, Brighton and Hampton.

Reddit user Callum posted a photo of the luminescent display at St Kilda caused by handfuls of sand hitting the water.