Watch: Napier ocean glows blue as seas subside and bring plankton light show to town

Blue moon?

How about blue ocean?

Westshore residents and curious passers-by were treated to a natural light show on Saturday night when the ocean off the seaside Napier suburb turned blue.

The natural phenomenon was captured beautifully on video by Codee Mavis Daley-Wilkins.

The blue light occurs when bioluminescence is present in the water, usually from an algae bloom of plankton.

The sea will glow but usually only when it's disturbed by a wave breaking or a splash in the water at night.

Calm and warm sea conditions are usually needed as well, for the phenomenon to occur.

Saturday night's sea conditions were just that, a far cry from the swells that pummeled Hawke's Bay's east coast in the last few weeks of March during a prolonged period of bad weather.

Witnesses to the blue light commented to Hawke's Bay Today on Facebook that it was "such a stunning still warm night to sit on the beach and watch this amazing, rare phenomenon''.

Mikayla Cooper described it as "absolutely beautiful ... never seen anything like it and it was wicked.''