Quote Originally Posted by tailingloop
In the waters I fish most often, both fresh and salt, the light absorption affect is often noticeable within a few feet of the surface, even with the sun overhead. There tends to be a lot of suspended particulate in the water. Divers visiting San Diego usually comment on the limited visibility and dull show below the surface unless they use some type of illumination.
Tailingloop, what you're describing is a little different. Particulate in the water such as algae blocks all light and makes everything dimmer. Light passing through gin clear water starts slowly losing the less energetic wavelengths, starting with red and progressing through blue/violet. Dirty water doesn't cause the color shift, although the water itself may be a different color. Think yellow snow-- there's no color shift, but it's a different color.

I dove San Diego and everything had a greenish hue due to the abundant algae in the water. At 30' depth the red bits of my gear still looked red, even though the world seemed rather green. At 100' my gear doesn't look red anymore but turns a dark purple, even in crystal clear water found in other places. That's the color shift effect.

MM