A lifeguard supervises the safety and rescue of swimmers, surfers, and other water sports participants such as in a swimming pool

Swimming pool

A swimming pool, swimming bath, wading pool, or simply a pool, is a container filled with water intended for swimming or water-based recreation. There are many standard sizes; the largest is the Olympic-size swimming pool...

, water park

Water park

A waterpark is an amusement park that features waterplay areas, such as water slides, splash pads, spraygrounds , lazy rivers, or other recreational bathing, swimming, and barefooting environments...

, or beach

Beach

A beach is a geological landform along the shoreline of an ocean, sea, lake or river. It usually consists of loose particles which are often composed of rock, such as sand, gravel, shingle, pebbles or cobblestones...

. Lifeguards are strong swimmers and trained in first aid

First aid

First aid is the provision of initial care for an illness or injury. It is usually performed by non-expert, but trained personnel to a sick or injured person until definitive medical treatment can be accessed. Certain self-limiting illnesses or minor injuries may not require further medical care...

, certified in water rescue using a variety of aids and equipment depending on requirements of their particular venue. In some areas, lifeguards are part of the emergency service

Emergency service

Emergency services are organizations which ensure public safety and health by addressing different emergencies. Some agencies exist solely for addressing certain types of emergencies whilst others deal with ad hoc emergencies as part of their normal responsibilities...

s system to incidents and in some communities, the lifeguard service also carries out mountain rescues, or may function as the primary EMS provider.
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.