A
lifebuoy,
ring buoy,
lifering,
lifesaver,
life donut,
life preserver or
lifebelt, also known as a "kisby ring" or "perry buoy", is a life saving
buoy designed to be thrown to a person in the water, to provide
buoyancy and prevent
drowning. Some modern lifebuoys are fitted with one or more seawater-activated lights, to aid rescue at night.