What additional factor becomes challenging to estimate in extremely clear water?

In extremely clear water, estimating distance becomes challenging due to the lack of visual cues that aid in perceiving depth and spatial relationships. In clear water, objects can appear to be farther or closer than they are because of the way light travels and how it refracts underwater. This phenomenon can result in a misjudgment of how far away a diver or an object may actually be, as the clarity can lead to a sense of perspective that is difficult to gauge.

While time, pressure, and flow rate are all important factors in a diving context, they are relatively more consistent and quantifiable through instruments and experience. Time can be tracked with a watch, pressure can be measured with a gauge, and flow rate can be evaluated with specific tools or by determining current patterns. In contrast, distance perception relies heavily on visual interpretation, making it more susceptible to subjective biases in clear water conditions.