A light task loading can be managed by the operator with capacity to spare in case of contingencies.
Ratings contain a large personal component and may vary considerably between subjects, and over time as experience is gained.
[5] This is particularly a problem in scuba diving, where the breathing gas supply is limited and delays may cause decompression obligations.
Task loading is generally increased by any unplanned demand on the diver's attention, such as an emergency, an adverse change in environmental conditions, or a deviation from the dive plan.
A diver learning how to use a dry suit, or starting underwater photography, or learning to operate a rebreather or manage multiple gas decompression will need to dedicate considerably more attention to the proper functioning of the new and unfamiliar piece of equipment which increases the risk of neglecting other critical responsibilities.