The surf is sparkling with neon light. Here’s where to see bioluminescence at San Diego County beaches.

Beachgoers are once again fanning out along the San Diego County coastline at night to watch the surf sparkle and flicker with enchanting blue neon light.

The phenomenon, which is sporadic and difficult to predict, is caused by bioluminescent plankton that light up when they tumble around in the surf or hit the legs of people walking in the ocean.

Initially, the bioluminesence was mostly confined to a handful of spots, including La Jolla Shores and Encinitas. But over the past few days, the bright flashes also have been reported at Point Loma, Sunset Cliffs, Oceanside, Tamarack Beach, Carlsbad Beach and Blacks Beach.

The flashes have been easier to see lately because there’s a waning crescent moon, reducing the amount of reflected light that hits the ocean at night.

Bioluminesence also can become more than visible when there’s strong surf. San Diego County beaches will receive waves in the 1- to 3-foot range on Tuesday night, with occasional sets to 4 feet. The waves will be slightly higher on Wednesday night, according to the National Weather Service.

Lifeguards urge the public not to venture onto low-lying rocks at night to view the light flashes because it can be hard to see potentially dangerous incoming waves.