Why are diving instruments more critical during deep diving?

Diving instruments are critical during deep diving primarily because depth, time, direction, and breathing gas must be constantly monitored to ensure diver safety and effective dive planning. As divers descend to greater depths, the potential risks and physiological effects increase significantly.

Monitoring depth is crucial to avoid exceeding safety limits related to nitrogen absorption and to prevent decompression sickness. Time management is equally vital, as it helps divers track how long they have been underwater, especially when adhering to no-decompression limits or planning for staged decompression during ascent. Direction becomes important to maintain navigational awareness in environments where visual references may be reduced or obscured. Lastly, monitoring the breathing gas composition is imperative, particularly as divers use different gas mixes or switch to specific breathing gases at certain depths to prevent toxicity or hypoxia.

The other options do not accurately reflect the needs during deep diving. Instruments are not lighter at greater depths, nor do they need to be replaced frequently simply because of depth. While navigation assistance is part of their function, it is not their sole purpose; hence the other aspects of monitoring are fundamental to the overall safety and success of deep dives.