It took four attempts for Stephen Bay to see the neon-blue waves crashing against the rocks at Torrey Pines State Beach, but when he did, just one thought went through his mind: "Holy cow, the waves are glowing!" he told NPR.
"They were just lit up in this incredible light that no photo can really do it justice," Bay, a professional photographer, said.
A red tide off the San Diego coast is behind the brilliant display of bioluminescence that is lighting up the water and drawing huge crowds to marvel at the rare phenomenon.
According to the Scripps Institute of Oceanography at the University of San Diego, the red tide is due to a cluster of dinoflagellates -- microscopic organisms -- that live in phytoplankton and light up when there is movement or they are disrupted.
The water-and-light show started on Monday and remained visible Tuesday night, "still beautiful," according to Bay, "but much less vibrant."
Bioluminescence expert Michael Latz said that local red tides like the one visible this week from Encinitas to La Jolla -- about a 20-mile stretch -- "have been known since the early 1900s due to observations by Scripps scientists."
Several Scripps scientists are collecting samples of the current red tide for future research on "the genetic and metabolic characteristics of the organisms."
It's not clear how long the current red tide will last; in some instances they've lasted from a week to a month or more. The last red tide in San Diego took place in September 2013 and lasted a full week. A similar event in October 2011 lasted a month.
Bay's advice: "Hurry up and get out there."