Which one of the following is NOT a benefit of enriched air diving?

The option indicating that increasing the total weight of diving gear is not a benefit of enriched air diving is indeed correct. In fact, enriched air diving typically involves the use of tanks filled with a higher percentage of oxygen than regular air, which does not inherently increase the weight of the diving gear itself.

In contrast, the other options highlight the positive aspects of utilizing enriched air. For example, the increased flexibility in dive planning arises because divers can spend more time underwater compared to those using regular air due to lower nitrogen levels, which leads to a reduced need for decompression stops.

Enriched air also facilitates longer dive durations, allowing divers to maximize their time spent exploring underwater environments. This is primarily due to the fact that with a lower nitrogen content, divers experience less nitrogen absorption, thus allowing for extended bottom times. Furthermore, the use of enriched air significantly lowers the risk of decompression illness compared to normal air since it reduces nitrogen exposure during the dive.

Thus, while enriched air diving provides multiple advantages related to dive planning, duration, and safety, increasing the total weight of diving gear does not fall under those benefits.