"As different colored light becomes limited, opportunities are created for organisms to exploit fluorescence to produce visual contrast and patterns. This is where it gets tricky. Biofluorescence is easily confused with bioluminescence, but they are very different things. Bioluminescence is like a DIY glow-in-the-dark. The organism emits its own light, which human eyes can see without any special filters. Biofluorescence is more like reflecting light, not creating light. This means that in order to biofluoresce, at least a little bit of light is necessary from a different source. To see fluorescence, a special filter is needed on your dive goggles, typically with a yellowish-tint."