Define the term 'emergency ascent'.

An emergency ascent refers to a situation where a diver must ascend rapidly due to a life-threatening scenario, such as running low on air or encountering a dangerous underwater condition. This type of ascent is characterized by its urgency and the need to prioritize immediate safety over standard ascent procedures, which typically emphasize controlled rates and gradual ascent.

In emergency situations, a diver may not have the luxury of descending safely or performing the recommended safety stops, which are usually designed to reduce the risk of decompression sickness. Therefore, understanding that an emergency ascent is a rapid response to a critical situation highlights the need for divers to be prepared for such circumstances and to know how to respond effectively when faced with potential danger under the water.

While other options might describe aspects of diving ascent practices, they do not capture the essence of an emergency ascent, which is fundamentally about responding urgently to an immediate threat.