life buoy

noun2

1. •
   (UK) A buoyant object (most commonly torus-shaped) that is used as a life-saving device by keeping a person afloat.

   • At least four approved ring life buoys shall be placed on each manned platform. — 1981
2. •
   (UK, figurative) Something that rescues one from difficulties.

   • Fearing that he might become permanently sewn into the Air France uniform he put on every morning, Manuel regarded Mario's faith in him as a life buoy. — 2001