Like a lot of my other spur of the moment trips, this started out with a post on Twitter. Someone down in San Diego mentioned that the ocean was blue. I had read about bioluminescent tide before, so I assumed that’s what was going on. This kind of thing only happens every few years, and I had never seen one before, so there was no way I was going to risk missing this, and I headed down the coast as soon as I could find time.

According to The Scripps Institute , these displays are caused by a bloom of dinoflagellates , a certain type of plankton. They glow naturally when bumped into or jostled around. The ocean itself doesn’t constantly glow, but waves do light up with a surprisingly bright blue light when they crash.

The plankton blooms that lead to these glowing tides don’t happen with any kind of regularity and aren’t predictable. Even the folks who study them for a living don’t have a real good way of predicting when they will appear or disappear, or how intense they will be.

As luck would have it, I heard the news a little late and showed up past the peak of the event. The bloom started on Monday, peaked on Tuesday, and was fading by the time I arrived on Thursday. On Friday night, there was nothing left anywhere along the coast.

From Twitter and Reddit, I got the impression that the bloom was moving north, so I got off the freeway at Carlsbad and worked my way south until I saw a shoreline packed with cars. Figuring that there was no other reason so many people would be at the beach at nearly midnight on a Thursday, I parked and walked to the shore.

As hard as it might be to believe, it actually does look like this. The blue is consistently visible to the naked eye, though you may have to spend a minute or two letting your eyes adjust to the darkness.

I need to get better at low-light photography. It took a while to find some aperature and shutter speed that worked, and I still had to clean up a lot of noise in post. Maybe that’s normal for these conditions, but after seeing photos like this or this or this , I can’t help but think I’m doing something wrong.

On a related note, I want to thank whoever it was who told me to shoot in RAW. Every picture I snapped would have been wasted if they were saved as JPEGs. If your camera gives you the option, I would highly reccomend shooting in RAW instead of any compressed format. Storage is cheap enough these days that there really isn’t a good reason not to, especially considering that many cameras are capable of saving images as both RAW and JPEG at the same time.

Unfortunately, there’s no real solid way of knowing when the next plankton bloom that leads to a bioluminescent tide will happen. If you live near the coast, you’ll need to keep your ears and eyes open and head to the shore as soon as you hear about blue waves to have a chance of witnessing one of these relatively rare events. You might be sleepy the next morning, but it’s worth it.