In which scenario is a diver advised to follow the rule of halves?

The rule of halves is a guideline used in dive planning to manage nitrogen absorption and provide a margin of safety, particularly during no-decompression dives. This rule suggests that divers should take their total dive time and divide it into halves if they exceed certain limits, allowing them to stay well within safer ascent profiles.

Having the option to apply this rule during any no-decompression dive is essential because these dives allow you to ascend directly to the surface without requiring staged decompression stops. The nitrogen absorbed in tissues during no-decompression dives can accumulate, and by adhering to the rule of halves, divers can mitigate the risk of developing decompression sickness. This means that as dive time increases, using the rule helps ensure that the diver is maintaining an appropriate ascent profile and minimizes the likelihood of nitrogen saturation leading to potential issues upon surfacing.

The other options may pertain to valid considerations for diving but do not necessarily align with the applicable use of the rule of halves as effectively as the scenario of no-decompression dives does.