Lifeguard (noun)

1. A person who is responsible for ensuring the safety of people in a swimming or recreational area.
2. A person whose job is to watch over swimmers and prevent accidents.

Origin:

1913, from life + guard.

Examples:

1. The lifeguard blew the whistle to signal that the pool was closing.
2. The lifeguard rescued the child from the deep end.
3. Lifeguards are trained to give first aid and CPR.
4. The lifeguard was on duty from 9am to 5pm.
5. Lifeguards are responsible for enforcing rules and regulations of the swimming area.