A scuba diver in the open water is immersed in clear, pure blue light. Water strongly absorbs red, orange, and yellow light, while blue light penetrates into the depths.
(Larry Madin, WHOI.)
The advantage of UV vision shows in reef views in visible (left) and ultraviolet (right) light. In UV light, the fish are in much higher contrast to the background.
Prey species like the copepod (Labidocera), are nearly transparent in visible light (left), but are brightly visible when photographed in polarized light (right), or to a predator that can see polarization of light.
DIVING INTO DIFFERENT WORLDS: Open ocean water (left) contains few particles and absorbs warm colors, so blue light penetrates far into the clear distance. Near the coast, high nutrient levels allow dense growth of phytoplankton (center), making the water appear green and darker (right). Forests appear dark and green for the same reasonplant pigments absorb red and blue wavelengths of light, and reflect remaining green light. (Left and inset by Larry Madin, right by Terry Rioux, WHOI. )