Glow In The Dark Shark

After 20 years of exploring St Brides Haven in Pembrokeshire, Lloyd Rees-Jones thought he had seen everything this shore dive had to offer, but he was soon proved wrong

St Brides Haven in Pembrokeshire, West Wales, is a location that is very special to me. It’s where my wife and I got engaged and subsequently married, it’s where I dive on a regular basis with my wife, father-in-law and father, it’s where I introduce novice divers to the wonders of the underwater world -and it’s the place I encountered my first UK shark.

I was very naive to think that all her secrets had been discovered, however her biggest secret to date she had kept hidden from us in plain sight. That shark that I encountered on my very first dive was special for another reason – it had the ability to glow in the dark. The only problem was that we were using the wrong equipment to see its true beauty.

My love for catsharks can be traced back to that first open water dive in 2006. My diving instructor Dutchy told me ‘Lloyd, you’re going to see sharks today’. And while he was demonstrating how to clear a fully flooded mask, a beautiful lesser spotted catshark glided out from the kelp behind him and rested gently on the sand between his knees. He completed the skill, looked down at the shark and smugly smiled at me through his regulator. I was instantly hooked, I mean, come on, sharks on a shore dive, surely it can’t get better than this – but wait, it does!

My journey into marine fluorescence started during lockdown. With most outdoor activities limited, I resorted to living vicariously through the diving adventures of others on social media. And this is when I discovered the amazing work of Scotland-based underwater photographer James Lynnott. James was quite literally shedding a new light (every pun intended) on our native marine life and I was captivated by this secret fluorescent world. I was keen to see if this was something that was only found in the Scottish sea lochs or if this could be viewed around the rest of the UK coastline. I began to talk to James to gather information on equipment, locations, depths, environments, tides and dates. He was even kind enough to offer me a ‘beginners bingo card’ of species to start my fluorescence journey.

Ultimately it was one species above all others that captivated me when it came to marine fluorescence, and that was the lesser spotted catshark. I was completely in awe of the fact that my favourite shark has the ability to glow in the dark and I had to find out more.

Now I don’t have an academic background, I’m just an underwater videographer who is passionate about the underwater world. I have a little knowledge to get by on the subjects that I film. There are far more educated individuals out there at the forefront of marine fluorescence who can provide you with a more-rounded understanding, such as Charles Mazel, Lynn Miner and Horst Grunz.

I can only provide you with a basic understanding of how it works. Some marine life and plants have the ability to absorb high energy levels of light and with the help of a special protein, they can re-emit said light on a longer lower wavelength, which under the right conditions and with the right equipment is visible as fluorescence. This is usually visible as neon green/red/pink/yellow or blue. After some time spent purchasing equipment and scanning through old log books, I narrowed down my dive site selection and headed to the beach with my trusty ‘bingo card’ and a new set of specialist blue video lights. We descended to the seabed and turned off all lights and allowed the darkness to wash over us. I activated the blue lights and was instantly taken back by what I saw.

The reef that I knew and loved was completely alien to me and I felt as if I had been transported into a psychedelic lava lamp. The kelp all around the reef had changed from green to red, the gem anemones were now a mixture of red, blues and neon greens, and the brown topknot had been transformed into a golden yellow with patches of red and green. I was overwhelmed with this new environment and I was keen to investigate it further. I set up my camera on its tripod along the edge of the reef and began to film some of the smaller species, like anemones and soft corals.

And then out of the corner of my eye, I noticed what looked like a green eel gliding through the kelp, and that’s when it came fully into shot. It seemed like it was moving in slow motion. A beautiful juvenile lesser spotted catshark with a vibrant green glow was heading straight for us.

Now I would like to say that I composed myself in that first interaction and that I calmly signalled to my buddy that we would be moving off, retrieved my camera and followed the shark around the reef. But that would be a lie. In all honesty I turned to my buddy, screamed through my regulator ‘shark!’, grabbed my camera and bounced off the seabed leaving a cartoon-style cloud of sand and debris behind me.

So, I know what you’re thinking, ‘did you get any good footage Lloyd’? Well… No, it was utterly unusable, almost as if I had never used a camera before. Settings were all wrong, the shark was out of focus and don’t get me started on the lights. One light was on full beam and the other on full spot and both lights were fully in shot.

But in my head, I had captured the best footage I had ever filmed and I was so confident that I ended the dive early as nothing else I was going to film on that dive would be as good as this first footage. After reviewing the footage on our surface interval over a large plate of humble pie, I came up with a new plan for our second dive. A plan I carved into my dive slate with a font so large there was no way I could miss it.

I was more relaxed in the water this time around and focused my attention on the edge of the reef around the snakelocks and gem anemones, spending time flicking between wide angle and macro photography. The fluorescent detail in the gem anemones was amazing to see up close. This bland-looking anemone is given a new lease of life under blue light and I was keen to see the variations available in other anemones.

With around 200 bar left in our cylinders, we headed off over the reef and out into the middle of the bay in search of catsharks. We passed over large fluorescent hermit crabs with a multitude of fluorescent adornments on their shells. As we headed back ashore, we came across three lesser spotted catsharks in various stages of maturity. Each shark was as beautiful as the last, with a shimmering fluorescent display akin to a neon green glitter ball.

These ‘glow in the dark sharks’ have ignited a curiosity in me. How many of our native shark species have the ability to produce fluorescence? Is this something only found in lesser spotted catsharks, or is this just the tip of the iceberg when it comes to fluorescence in sharks?

Over the past few years, I have been documenting as many species as possible around the Welsh coastline, with beautiful vibrant displays in some species and some sharks producing no fluorescence at all. So, I started to look into the lesser spotted catshark fluorescence in more detail. Why was I seeing two distinctive patterns on these sharks?

Most catsharks had a vibrant shimmering glow while others produced a lacklustre mottled dull glow. Others have theorised that this colour difference in males and females could be a way for them to identify each other in the dark and find a mate. I have my own theories, but some of them are a little far-fetched, so for now I’m happy to keep them to myself until I can test them out further. In the meantime, I will keep admiring the sharks, but there is more wonder to be seen in this new world of underwater fluorescence.