It's a case of the Hong Kong blues.

The sight of the waters off Hong Kong these days can take your breath away.

But, the haunting fluorescent blue seas are also deadly dangerous to marine life and potentially to humans.

The glow is a kind of red tide that is caused by an algae marine biologists call "sea sparkle," a rare organism that can act both as animal and plant.

The algae looks red in the daytime but shows up blue once the sun sets.

Scientists say the beautiful blue algae is linked to chemical run-off from farms and sewage from businesses.

They warn it's a growing global problem that could eventually boost the amount of harmful toxins in the human food chain.

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