Underwater, the Red Sea offers a kaleidoscope of colour, but I never expected blue, orange and inky black to produce the most fluorescent greens I have ever seen.
Yet this was the result of the most unique of night dives.
I had seen the sun-bleached poster at Sinai Divers, and thought the Blue Light Night Dive would be a different Sharm experience.
I was handed a blue torch - yes a torch with a blue beam –and had an orange visor cable-tied to my mask.
Trudging to the water’s edge, the bright lights of Na’ama Bay illuminated the skyline.
But they were about to be dimmed by a unique ‘glow in the dark’ underwater perspective, normally invisible to the naked eye.
Now, we all know that the reef changes come nightfall and a pinnacle that looked spectacular in the sunlight would be almost unrecognisable in the darkness as the coral burst into life from its daytime slumber.
But cruising above the sandy bottom of the bay just a few metres beneath the surface, a lone anemone signalled what we the sea was about to reveal.
Most divers would most likely glide past the lone animal. But illuminated by the bright blue torch beam, and filtered through our orange visors, the tips of the fronds glowed a brilliant green as they wafted in the gently swaying water.
This was not just any old green, but a bio-fluorescent green brighter than the dials of our gauges.
Now the science bit.
Studies have found some corals fluoresce, thanks to a physical and chemical reaction involving proteins in the animal. Researchers believe many cnidarians fluoresce in green, blue, yellow and red colours and this gleaming originates mostly from special protein structures.
This is normally invisible to humans, because it operates on a wavelength beyond what our eyes can typically perceive. So we adapt.
During fluorescence, special pigments (proteins) absorb short wave, energy rich (UV-) radiation (the blue bioluminescent light)and redistribute it nearly simultaneously – however with a higher wavelength which lies in the visible spectra and seen as green through the orange visor.
The Green Fluorescent Protein was first discovered in bioluminescent jellyfish in the 1960s. Half a century later, scientists are still trying to work out why.
But are they acting as sunscreen, protecting the coral from the sun’s harmful rays? Or converting the energy of the sunlight into light that can drive photosynthesis? Are they providing a beacon to coral life that can detect light?
Researchers have found that certain zoooxanthellate (algae housing) corals are able to thrive below the euphotic zone through auto-fluorescence. In the Gulf of Aqaba, the zooxanthellate coral Leptoris fragilis has been found living at a depth of 145 m – depth in which no photosynthetically active light can penetrate. Though, specific pigments in the coral tissues catch the remaining UV light. These UV radiations are shifted / diverted into photosynthetically active radiations which can be used by the zooxanthellae (algae) for photosynthesis.
But back to the dive.
My enthusiastic guide, Slovak Jan Karpis, told me it would be a darker night dive than normal. It took a few minutes to get used to the reduced visibility as the orange filter removed the ambient light.
But once we arrived at a coral block it didn’t matter.
As our specially made blue torches flicked across the reef the illuminated certain corals with a brilliant green. The favites was so bright, it looked like someone had switched a light on inside.
As the tentacles of an anemone swayed in different shades of green, an occasional flash of dark moved between them. Apparently this was the fish but because not all fish fluoresce, we were told that we would see very little in marine fauna. There only trace was as they crossed in front of the beams of our lights.
But who cared when the coral gave off such tremendous colour?
If this was on land, this ‘glow in the dark’ treat would be the tacky neon streets of Las Vegas, but underwater, the beauty of the reef was tremendous.
And it wasn’t just green. Some of the corals glowed a stunning orange or red.
The luminous green also helped find the critters, tiny nudibranchs became easy to spot as they flashed brightly.
A coral pinnacle that one would glide across at daytime kept our attention for the full 50minute dive.
But beware, even though we were using blue lights, lionfish were still attracted to us.
Lifting the visor away long enough they could be spotted swimming just beneath us, piggybacking divers to help with the hunt and hoping the light would illuminate a passing fish for lunch.
Afterwards, I asked Jan for his thoughts on the natural wonder. He admitted that the whys didn’t matter to him, it was the wonder that kept him jumping back in the water every Friday night.
And with this wonderful light display, who could blame him.