Fluorescence diving (also know as UV, fluoro or glow diving) is a spectacular form of night diving that uses specialist dive lights or a white light filter and a mask filter to see the colourful display put on by corals, invertebrates and even some fish. The light used in fluoro diving equipment brings out the vibrant colours reflected by certain proteins in living organisms, making them appear in bright green, yellow, red, purple, pink or blue hues.
Unlike phosphorescence (the glowing pieces on a watch or the dials of a depth gauge) which has the capability to store light and re-emit it over a longer period of time, fluorescence absorbs high-energy light and re-emits it immediately as low-energy light. To see fluorescence you need a dive light that emits blue light and because our eyes aren't built to see the emitted light you'll also need a special yellow filter that fits over the lenses of your mask and also one for your camera if you like to take photos or record video.
It is possible to source the appropriate colour filters needed and build a filter for your existing white light dive torch but it is never anywhere near as effective as a dedicated blue light. The blue light is over a very close spectrum whereas white light is over a broad spectrum. Applying a filter will give you the spectrum needed but the brightness it provides is significantly less than a dedicated light using a blue LED, something like 80% of the light generated by a normal white LED would effectively be wasted. This video demonstrates the difference between using a filtered white light and a blue light.
Scientists have known about the fluorescent properties of coral and marine creatures since the late 1920’s. They understand how it works but don't currently know why certain marine life produces these colours.
Whilst we may not fully understand why the light is re-emitted, scientists have been able to start to use the phenomenon to monitor the health of reefs as fluoro lights can reveal the early onsets of coral bleaching, or show the extent of destructive algae contamination.
