A long, dark shadow crept quietly, imperceptibly across the sand flat. The sun was setting behind Catalina Island, the kelp forest was going dark, and I was witnessing an incredible sight. As day turned to night thousands of creatures were returning home, seeking shelter in the rocks and kelp, a safe place to rest. Everywhere I looked there was activity; a bat ray circled lazily, sheep crabs scurried, and fish were disappearing. Sensing the coming darkness, a solitary lobster marched defiantly across the open sand just a few feet in front of me.

But with all of this, it was the blacksmith fish that had dropped me to my knees. I watched transfixed as hundreds, no thousands, of these shimmery fish materialized out of the darkening ocean. As I scanned the limits of the 50-foot visibility, I could see them swimming furiously, materializing from all directions, toward an undefined point. There, they formed into an unending parade of fish determinedly entering an unseen portal in the edge of the kelp forest.

The minutes slipped by. My dive table advanced with the shadow, from N to O to P, yet the parade of blacksmith continued. As I watched this fascinating sight, the shadow overtook me and twilight turned to night.

Twilight, quite possibly is the most incredible time to spend time in the ocean. It certainly is my favorite dive time. We divers spend a lot of time talking about and defining dive sites, but what about dive times? When is that favorite dive sight best to dive? I think back on the many twilight dives I have enjoyed, “Gull Island” near Santa Cruz Island, “The Gap” at Anacapa, Redondo Beach, and many others. But this dive, at “Hen Rock” off Catalina Island capped them all.

At sunset and sunrise the ocean goes through a transformation. The fish and other diurnal creatures have spent their day foraging through the reef and kelp forest, venturing out into the deepening waters of the sand flats. As the sun sets and shadows creep across the rocks and sand, these daytime animals search out a safe haven to rest for the night and allow the nocturnal creatures their turn to forage and interact. At sunrise the whole process reverses once again. An easy forty-five minute dive at almost any favorite dive site is ample time to watch the full transformation. The trick is to time it right: going down in the last few minutes of sunlight, just before the sun dips behind the island and the shadows begin to grow, and coming out after darkness has fallen across the ocean.

As you settle into neutral buoyancy in those last fifteen minutes of daylight, familiarize yourself with the site. The macro views and the micro views, but take notice more of the critters than of the features of the reef. Get to know who is out and about and who is lurking in the crevasses. As the next fifteen minutes of twilight’s shadow moves across the landscape, note how the animal behavior changes. Nonchalance is replaced by determination, feeding is replaced by a search for shelter. And then it is night. Every diver who has spent time on a darkened reef knows what a magical place it is. Maybe you will even catch a phosphorescent light show on the way back to the surface.

With the recounting of my dives at Hen Rock it is my intention to point out that there may be an aspect of pre-dive planning that more divers fail to consider—when to dive. We discuss where to dive, our favorite sites, the topography of the reef. We discuss how long we will be down and what we expect to see. But how many times have you overheard two buddies deciding when to dive?

I have found that revisiting a favorite dive site is fascinating. Each time I get to know the nooks and crannies, the valleys and rocks, and the creatures a little bit better. But to really know a site you must experience all the aspects of that site. See it in daylight. See it after dark. But best of all, watch it transform from one to the other.

After spending nearly fifteen minutes on my knees in the sand that day at Hen Rock, I realized as I turned on my flashlight and swam away that I had not ever seen the end of the parade of blacksmiths. I guess I’ll just have to go back there soon and watch it again.

Andrew Lee is a Southern California Divemaster with hundreds of logged dives throughout the Channel Islands.