The non-toxic phytoplankton is not considered harmful and is relatively common in Hong Kong. What is uncommon is capturing its iridescent glow on camera, which only appears when the water is disturbed.
Local photographer Lit Wai Kwong also took an image of the phenomena at Tai Po in Hong Kong's New Territories.
"You can see the blue light if there is a wave, a boat moving, or a stone thrown in the water," said Kwong, who used a 30-second exposure to get the shot.
"There was no blue light when the water was calm, therefore many people threw stones into the water in order to see it."
Despite its blue hue, the phenomena is referred to as a red tide and, according to a Hong Kong government website
that keeps track of sightings, several have been reported so far this year.
Michelle Cheung from the city's Eco-education & Resources Center said the bloom was caused by high pollution in Tolo Harbour, which was exacerbated by the slow flow of currents.
She said nutrient levels are typically high in the region, due to restaurant waste and sewage running direct from village houses into the sea.
Cheung added that the algae can be deadly because it deprives the water of oxygen, though the government has not recorded any evidence of fish kills.
"Hong Kong and the entire Pearl River Delta has a big problem with wastewater, and that is surely a factor with these plankton blooms," said David Baker from the Swire Institute of Marine Science at the University of Hong Kong.
He said, by itself, Noctiluca scintillans doesn't represent a threat to human or environmental health, but the huge bloom does represent an ecosystem that's "out of balance."
"I guess the analogy is they're like locusts that feed on agricultural crops. And once they find a good abundant food source they will multiply until the food source is exhausted. In Hong Kong unfortunately most of the nutrients are coming from our own sewage."
The damage done to the environment doesn't just happen when oxygen is depleted during the algae's short lifetime.
When the blooms die, they sink to the bottom of the sea when they decompose, consuming huge amounts of oxygen.
"That's when we have the formation of these dead zones, where anything that's living, any fish or crab species living on the bottom, is at risk of dying from the low oxygen associated with that decomposition," Baker said.
Hong Kong has a number of zones that suffer from persistently low levels of oxygen, which "increase in their severity and their scope whenever we have these algal blooms," he added.