Figure 14. Heuristic illustration of the effect of fluorescence on the appearance of the swell shark, simulated from the perspective of other swell sharks.

The left column shows the appearance of the shark based on the reflectance spectra of the skin and ambient light; the right column shows how the appearance changes when fluorescence is emitted due to excitation by narrowband light. The blue colors in each box are the RGB renderings of ambient light at that depth simulated using in situ irradiance measurements⁶⁵ from Eilat, Israel (the most comprehensive published depth-gradient spectral data currently available). The white and gray patches in each shark drawing are scaled to show relative contrast rather than absolute colors. This illustration demonstrates that if the patches of the shark skin did not fluoresce, the contrast between the light and dark patches diminish with depth and the shark would match the background at depth. Fluorescence increases contrast between the dark/light patches of the shark by providing light spectra not naturally present in the blue ocean environment.