Psychedelic. Surreal. Trippy. Mind-Bending. Bizarre. Or simply awesome! I have heard numerous superlatives to describe the experience, having introduced many divers to fluo-diving. The normal reaction upon surfacing is sheer amazement that the reef can glow like it has just been plugged into the mains supply.

So why is it so different from a standard night dive? What can you expect to see? Is it really worth skipping cocktails at sunset on the beach?

GreenMagnificent sea anemone, mantis shrimp, corallimorph. All photos Alex Tyrrell

For your first fluo-dive, if possible, I would suggest diving on a coral reef to experience the full kaleidoscopic effect. When the beam from your light first makes contact with a fluorescent coral you will simply be amazed as to the colours that you see, in such stark contrast the normal muted-brown hue that the majority of hard corals possess. 

The most common colours that are emitted are bright greens, generated by the green fluorescent protein, but when the initial wow-factor subsides (this may take a dive or two!) and you start looking a little closer, you will begin to notice other colours too – oranges, yellows, purples and even red that is generated by chloroform that is contained within certain algae.

 CrittersTwo horn box crabs, spiny devilfish, decorator crab

Fluorescence also has the effect of revealing hidden creatures that you most certainly would have overlooked if using white-light, swimming by blissfully unaware of their existence. It is like have ultra-enhanced vision! Tiny nudibranchs, microscopic sand anemones, minuscule crabs and shrimps suddenly become visible and easy to spot, the neon glow negating the camouflage that evolution perfected over the aeons. 

Certain fish will also fluoresce; Scorpionfish in red, Goatfish in green, Triplefins in orange and if you are lucky to spot the right type of moray eel, they are a vivid glowing yellow! A lot of crustaceans fluoresce, as do anemones and the reef-building hard corals. A general guideline, though there are exceptions, is that the more dull coloured organisms fluoresce brighter than already brightly coloured creatures.


The dive, in general will be a darker than a normal night dive, as you are only using a narrow band of the light spectrum (blue) and then with the mask visor in place, you effectively eliminate your light source leaving only fluorescence visible.

It goes without saying that you need to be comfortable with night diving and have excellent buoyancy control to ensure you do not cause damage to fragile marine organisms or accidently spike yourself on an urchin!

That doesn’t mean that it is pitch black, though, as if you are diving on the reef the majority of hard corals fluoresce well, so ambient light levels are greater. But if you are diving in areas with less dense coral coverage, like a muck site, then there is less fluorescence or at least much smaller fluorescent subjects, so light levels are not so bright. But don’t rule out this environment for a fluo dive, there are chances of finding fluorescent surprises hiding in the sand, a glowing spec in the expanse of darkness that could be a new fluorescent discovery.

So why not skip that cocktail and get out there and see what subaquatic fluorescence wonders are awaiting you?



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