Night diving the SS President Coolidge is already one of the most iconic wreck experiences in the world—but when flashlight fish appear, it becomes something entirely different.
As you move through the dark corridors of the wreck, your torch catches brief flashes of green light. Then more appear. Suddenly, you’re surrounded by small glowing fish, blinking in the darkness like drifting signals from another world. These are flashlight fish—one of the ocean’s most unusual bioluminescent species—and the Coolidge is one of the rare places where divers can reliably encounter them.
In this guide, we’ll explore what flashlight fish are, why they glow, and why the SS President Coolidge in Espiritu Santo, Vanuatu offers one of the best opportunities in the world to see them on a night dive.
What Are Flashlight Fish?
Anomalopidae—better known as flashlight fish—are small, short-bodied fish with a dark charcoal-grey colour, large eyes, and subtle white markings near their fins. Growing to just around 12 cm / 4.7 inches, they might seem unremarkable at first glance.
But that changes completely after dark.
Beneath each eye sits a specialised light organ called a photophore, filled with millions of bioluminescent bacteria. These bacteria produce a bright green glow—so powerful it can be seen from over 30 metres away in total darkness.
What makes flashlight fish truly fascinating is their ability to control this light. Using a dark membrane, they can “blink” the glow on and off—up to 75 times per minute. This isn’t random behaviour either. These blinking patterns are used to:
- Communicate with other Flashlight Fish
- Attract prey
- Confuse predators
For years, scientists believed flashlight fish were solitary. But more recent observations in the South Pacific have shown them working together—using their bioluminescence to coordinate movement as a group when hunting or avoiding danger.
Image Credit to Diver Hiro from the article: An Illuminating Discussion about the Flashlight Fish.
Where Can You Find Flashlight Fish?
Flashlight fish are found throughout the tropical Indo-Pacific, including waters around Thailand, Indonesia, the Philippines, New Caledonia, and Vanuatu.
They are typically a deep-water species, most commonly inhabiting seaward reefs between 15–50 metres (50–164 feet). During the night, some individuals move into shallower areas to hunt small crustaceans, while during the day they retreat into dark, sheltered environments such as caves, crevices—and wrecks.
Wrecks like the SS President Coolidge in Espiritu Santo, Vanuatu.
Flashlight Fish on the SS President Coolidge
While flashlight fish can be found in a handful of locations globally, sightings are often unpredictable.
On the SS President Coolidge, they are as close to guaranteed as it gets.
Hiding deep within the darker sections of the wreck—particularly Cargo Hold 1 and Cargo Hold 2—these fish have made the Coolidge their home. During the day, they are rarely seen and quick to retreat from torchlight. But at night, in the absence of ambient light, they emerge.
And that’s when the magic happens.
Hovering in the blackness of the wreck’s corridors, their blinking lights create what can only be described as an underwater constellation—alive, moving, and completely mesmerising.
Requirements for Night Diving on The Coolidge
This is not a casual dive—and that’s exactly what makes it so rewarding.
Flashlight fish are typically found in deeper sections of the wreck, and the dive involves:
- Limited visibility
- Depth
- Overhead environments
To ensure safety and enjoyment, this experience is suited for advanced certified divers who are comfortable in these conditions.
Divers are also required to have completed at least one prior dive in Cargo Hold 1 or Cargo Hold 2 for orientation.
Additionally, to avoid disturbing the fish, torch use is carefully managed. Lights are dimmed or covered when entering the wreck, creating a low-light environment that requires good awareness and control.
A True Bucket List Experience
There are many great dives around the world. But drifting through a historic war wreck, in near-total darkness, surrounded by living, blinking lights—that’s something else entirely.
The combination of history, environment, and rare marine life makes this one of the most unique dives you can do anywhere.
If you’re looking for something beyond the ordinary—something you’ll still be talking about long after you leave Vanuatu—this is it.
Join us for a night dive on the SS President Coolidge and witness one of the ocean’s most extraordinary light shows for yourself.
Divers must be at our shop at Million Dollar View resort at 5:00 – 5:30pm (depending on the time of year) and the dive usually finishes at around 7pm.
To book your bucket-list dive, get in touch with us today. Trust us—you won’t be able to stop talking about it.
