Lifeguard

Noun

 * 1)  an attendant, usually an expert swimmer, employed to save swimmers in trouble or near drowning at a body of water
 * 2) a lifesaver
 * 3)  a sturdy metal bracket affixed in front of each of the leading wheels of a train to deflect small objects away from the wheels to prevent derailment.

Thesaurus
air warden, air-sea rescue, attendant, caretaker, castellan, coast guard, conservator, curator, custodian, forest ranger, game warden, gamekeeper, governor, guardian, guardian angel, janitor, keeper, lifeboat, lifesaver, next friend, prochein ami, ranger, rescuer, savior, shepherd, steward, warden, warder