Red tide: Electric blue waves wash California shore - BBC News
Glowing blue algae have transformed California's coast.
A dazzling neon blue tide in San Diego, California, has filled its beaches with electric aqua colours.

By day the plankton turn the water red, but come nightfall they radiate a blue glow when the algae are disturbed by movement, such as waves crashing on to the shoreline.

Bioluminescent light shows are not uncommon globally, but the last red tide in San Diego was in 2013 - and it's no less beautiful each time they grace the oceans.

See more images here