About Fluorescence

What’s Fluorescence All About?

Fluorescence is a phenomenon that occurs when we shine blue, near UV lights on the corals. Some of the corals have a certain protein that absorbs the blue light and re-emit the light in a different wavelength (colour). This causes the corals to glow in the most amazing colours like green, yellow, orange and some even pink or red.

Not only do the corals around you radiate a spectrum of the brightest fluorescent colors but so too does the aquatic life. Moray eels, crabs and tiny shrimps display flashes of a bright fluorescent yellow and scorpion fish luminesce with pink.

Why some corals and marine creatures fluoresce remains a mystery and there are still many questions to be answered. Scientists have various theories but none of these have been proven.

UV Dive Koh TaoCould it be that the corals are protecting themselves from sunburn and coral bleaching? Does the fluorescence help the corals with photosynthesis in dark places?

Funny thing and quite mysterious as well is that some separate corals of the same species right next to each other might display two different colors or one might fluoresce and the other not at all. Every dive again we realize how fascinating our surrounding reefs actually are.

Do the anemones lure food into their stinging tentacles by attracting them with the fluorescence? What is the reason that a shrimps’ pinchers shine a fluorescent yellow? How come a scorpion fish that does its utmost to blend in with its surroundings emits a bright pink colour under a UV light? Some scientist and researchers speculate that the fish could be communicating through fluorescence.

Some scientists among who pioneer, and expert in fluorescence research Dr. Charles H. Mazel, PhD, think that fluorescing corals might indicate the health state of the coral reefs. This fact is fascinating and makes the UV dive experience a very interesting way for coral researchers to indicate the overall health of a coral reef.

As you can see there are many questions yet to be answered and the reasons for fluorescence are still mysterious. One thing however is for sure: It is an unforgettable spectacle to witness!

What can you expect to see?

UV Dive Koh TaoThe UV Dive experience is a mind blowing tour over an amazingly bright glowing reef which is stunning just by itself, but once you get closer and closer to the reef or the sandy bottom you notice that the rabbit hole is much deeper than you think at first.

Spotting interesting fishes and critters during the daytime is one thing but during a UV Night Dive things work a little bit different. Swaying bright coral polyps are fascinating to look at from a close up angle and tiny shrimps jump and dart over the corals like an astronaut on the moon. Little orange crabs run over the sandy bottom and dig themselves in the sand once they realize they are being watched from above. Other little crabs sit in-between the corals while their fluorescing filters move swiftly up and down their mouth to feed.

The creatures that steal the show with their colours during the day, might not do anything special under a UV light. Contrary the ones that do their best to stay hidden and camouflaged during the daytime sometimes are the ones that stand out the most. Finding a family of glowing pink scorpion fish can be so mesmerizing that you just can’t stop staring at them.

UV Dive Koh TaoMacro lovers will absolutely love this dive because there is a whole new world out there. Things that you can hardly see during the daytime, all off a sudden get visible during a Fluo Night Dive. Under a blue light, Macro diving gets a whole new definition.

Searching in between corals for sleeping wrasse or goatfish can be quite rewarding as they radiate a bright yellow. Also little nocturnal moray eels come out hunting and look like radioactive snakes crawling over the bottom and in between the corals.

By now we have done quite some UV night dives around Koh Tao and I think we can safely say we are specialized in UV diving. We know exactly what to look for and what to point out. Although we know much of the fluorescing abilities of the reefs here, we keep discovering new things underwater that appear to be fluorescing so be prepared!

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