A ring-shaped device used as a flotation aid. Two types may be distinguished, based on their form, intended role and context in which they appear:
* [[Innertube]] - Air-filled and intended for recreational use. May be varicolored, or semi-transparent
* [[Lifebuoy]] - Made of a durable foam and intended for life-saving in emergency situations. Usually colored red, white, or in alternating red and white bands.