A swim ring (also known as an inflatable lifebelt, swim tube or rubber ring) is a toroid-shaped (hence the name "ring") inflatable water toy.

Swim ring
Swim ring method—a cost-effective alternative for prevention and healing of back ulcers
An Infant Presenting with Transient Consciousness Loss after Inappropriate Baby Swim Ring Use in the Bathtub
Swim ring for an infant
Ring-Necked Pheasants Can Swim
Egg oiling to reduce hatch-year ring-billed gull numbers on Chicago's beaches during swim season and water quality test results.
Floating aquarium for ponds comprises transparent dome which is filled with water and is mounted inside buoyant ring, fish swimming ...
We Went for a Swim at Midnight and Billy Proposed with a Ring .. I Said Yes; EXCLUSIVE: IN HER OWN WORDS, HOW LOVESICK KELLY & BILLY...
Swimming ring
Shape recovery and anomalous swelling of steam-compressed wood by swimming ring-like expansion of cell lumina