A buoyant ring carried on board ships that can be thrown to someone in the water in an emergency to keep themselves afloat.
An attendant, usually an expert swimmer, employed to save swimmers in trouble or near drowning at a body of water.
A lifesaver.
A sturdy metal bracket fixed in front of each of the leading wheels of a train to deflect small objects away from the wheels to prevent derailment.
A bodyguard or unit of bodyguards, a guard of someone's (especially a king's) life or person.