What type of visibility change should divers be aware of when using enriched air?

The correct choice highlights an important aspect of diving with enriched air, specifically related to color perception under increased partial pressures of oxygen. When divers breathe higher concentrations of oxygen, such as those found in enriched air Nitrox, it can lead to changes in how colors are perceived. This alteration is primarily due to the increased partial pressure of oxygen affecting the visual system, which can cause certain colors, particularly reds and greens, to appear differently.

This phenomenon is crucial for divers to understand, as it may impact their ability to distinguish colors while submerged, particularly in low-light conditions. Being aware of these changes can help divers make better decisions regarding their dive environment and enhance overall safety.

In contrast, the other options do not accurately reflect the relationship between enriched air and visibility. Claiming that visibility improves significantly underwater or that there are no changes in visibility does not account for the physiological effects of breathing enriched air. Furthermore, suggesting that lighting does not affect visibility when using EANx ignores the well-established fact that lighting conditions always have a significant impact on underwater visibility, regardless of the gas mixture being used.