Lifeguard:

A lifeguard is an emergency service worker who is responsible for overseeing the safety of the users of a recreational water feature, such as a swimming pool, a water park, or a beach. Lifeguards are qualified strong swimmers, trained and certified in water rescue, first aid, and cardiopulmonary resuscitation and sometimes in the use of automated external defibrillators, oxygen administration and specialized equipment for airway management or aquatic rescue.

Ocean lifeguard:

On shore, an ocean lifeguard can typically be seen watching the water from an elevated chair or tower, or patrolling the water's edge on foot or with a four-wheel-drive vehicle. Some of the better equipped lifeguard services operate inflatable or rigid hulled patrol boats that can provide added support in the event of a rip current situation or other emergency. Additionally, some also have rowboats, and specially marked personal watercraft equipped with a rescue 'Sled' (a reinforced oversize bodyboard to bring victims onto) available to respond from the beach.
An individual lifeguard tower will typically be staffed with one or two lifeguards responsible for a specific length of beach. Equipment used will vary depending on the area. This will normally include communications equipment and a well stocked first aid kit. Additional equipment may include a large long spine board, an oxygen resuscitator, an Automatic External Defibrillator (AED) or simple scuba diving equipment. A lifeguard vehicle or patrol boat will be equipped with two way radios and may also carry cardiac care medical equipment, an oxygen tank, and more advanced scuba gear.
Lifeguards are a critical component in providing emergency care until EMS arrive.
In some communities, the lifeguard service also carries out mountain rescues, or may function as the primary EMS provider.

Lifeguard duties

A key part of any lifeguard's mission is the prevention of in-water (as well as on-land) incidents. Therefore, one of the most useful measures of the effectiveness of a lifeguard force is not the number or rapidity of rescues, or the skill with which they are executed, but the absence or reduction of drownings, accidents, and other medical emergencies. While the ability to save lives is of paramount importance to lifeguards, the ability to prevent life-threatening situations is nearly as important.
Many young people in high school and college see lifeguarding as an enjoyable and rewarding part-time or summer job. Lifeguarding requires that one be constantly alert for any dangers to the patrons of the area under supervision. Like many other jobs, lifeguarding requires quick decision-making and communications skills. The primary duty of a waterpark, waterfront, or pool lifeguard is the safety of the patrons or swimmers. This primary duty includes water surveillance and rule enforcement, as well as rescues and first aid when required. Secondary duties include filling out incident report forms after accidents or injuries, ensuring safe and clean facilities are maintained, answering questions that patrons might have (rule concerns or directions), and in-service training to maintain lifeguarding skills.
While performing patron surveillance (usually from an elevated stand or a water-level standing or sitting position) lifeguards watch for and recognize struggling or drowning swimmers, and swimmers with sudden medical conditions such as a stroke, heart attack, asthma, diabetes, or seizures. Proper patron surveillance is key in preventing injury or death by drowning. Lifeguards should look for swimmers in these categories and conditions:

• Swimmers who are inactive in the water, submerged or otherwise (Passive drowning victim). When a lifeguard sees this kind of swimmer he performs an emergency rescue.
• Swimmers who are taking in water while attempting to stay at the surface (Active drowning victim). Lifeguards look for swimmers in this condition by looking for arms flailing vertically, with the body vertical and no supporting kick. This behaviour is known as the instinctive drowning response. Lifeguards perform an emergency rescue to assist this kind of swimmer.
• Swimmers who have become tired and are having trouble swimming (Distressed swimmer) and may or may not be calling out for help. Lifeguards usually swim out and help these swimmers to the side. They may or may not require additional assistance.
• Normal swimmers (Healthy swimmers).

Problems may occur at any time, so a lifeguard must be in good physical and mental condition in order to pull someone from the water and possibly perform rescue breathing, CPR, or first aid.
Lifeguards also are trained in first aid. Before administering first aid, lifeguards perform an initial assessment, and then a secondary assessment with the acronym SAMPLE.

• S stands for signs and symptoms. Lifeguards will try to find out what happened and where the patron feels any pain, discomfort, numbness, or loss of sensation.
• A stands for allergies. This is to find out what allergies the patron might have.
• M stands for medications, such as what medical conditions they have or what medications they have taken in the past 24 hours.
• P stands for pertinent past medical history. The lifeguard will try to figure out if the patron has experienced any recent falls, accidents or blows to the head, or if they have been in any medical, surgical, or trauma incidents.
• L is for last oral intake; what and when the patron ate or drank.
• E is for events leading up to the incident. What the patron was doing before the incident and what they were doing when the incident occurred.

Lifeguarding is not the same as instructing swim lessons, although (at pools) most lifeguards are instructors and vice versa.