Which of the following is NOT part of "Rule Number One" for divers?

The principle of "Rule Number One" for divers emphasizes the importance of managing one's breathing while underwater. This rule includes key practices such as breathing continuously and never holding your breath, as these are vital for preventing potential injuries associated with pressure changes, like lung overexpansion.

Exhaling forcefully during every ascent is not part of this foundational rule; while it's essential to exhale during ascent to prevent holding your breath, the emphasis of "Rule Number One" lies more on maintaining a continuous, steady breath rather than forceful exhalation. Forceful exhalation can sometimes be counterproductive or unnecessary, as it may lead to hyperventilation or discomfort.

In contrast, checking equipment before a dive is crucial but is not encapsulated in "Rule Number One," as it pertains more to overall dive preparation and safety rather than specific breathing practices while underwater.