A lifeguard is responsible for the safety of people in an area of water, and usually a defined area immediately surrounding or adjacent to it, such as a beach next to an ocean or lake. The priority is to ensure no harm comes to users of the area for which they are responsible. Lifeguards often take on this responsibility upon employment, although they can also be volunteers.

The conditions resulting in drowning are summarized by the drowning chain in which each link can lead directly to an incident, or contribute to a succession of links. It consists of lack of education about water safety or local conditions, a lack of safety advice (for example, about rip currents at a beach) a lack of protection (like no flotation device for a weak swimmer), lack of safety supervision, or an inability to cope with conditions (strong surf with a weak swimmer).

The drowing chain provides a clear basis for preventing drowning which includes:

·       education and information

·       provision of warnings

·       denial of access

·       supervision

·       training in survival skills

The lifeguard is able to provide all these elements to help prevent drownings (or other incidents) in their area of responsibility, and for this reason this should be the primary focus of a lifeguard's activities, as it is better to stop an incident occurring than trying to react once it has occurred. This means that the effectiveness of a lifeguard unit can be measured not by the number or rapidity of rescues, or the skill with which they are executed, but by the absence or reduction of drowings, accidents,  and other medical emergencies, Prevention is an effective skill that is vitally important to a lifeguard because it can aid in maintaining the safety of the aquatic patrons.