SDI Open Water Scuba Diver Practice Exam 2026 - Free Scuba Diver Practice Questions and Study Guide

As you descend underwater, colors are absorbed by the water at different rates, leading to the phenomenon of color fading. The first colors to fade as you go deeper are reds and oranges. This is due to the fact that these wavelengths of light are longer and are absorbed quickly by water. By the time you reach a depth of about 10 meters (around 33 feet), red light is significantly diminished, and shades of orange will also begin to disappear.

In contrast, blue and purple wavelengths are shorter and penetrate deeper into the water before being absorbed. This is why underwater environments primarily exhibit shades of blue as depth increases. The understanding of how colors disappear underwater is crucial for divers when it comes to equipment selection, photography, and understanding marine environments.