Nautical . a distinctively shaped and marked float, sometimes carrying a signal or signals, anchored to mark a channel, anchorage, navigational hazard, etc., or to provide a mooring place away from the shore.

a life buoy.

to keep afloat or support by or as if by a life buoy; keep from sinking (often fol. by up )

The life jacket buoyed her up until help arrived.

Nautical . to mark with a buoy or buoys.

to sustain or encourage (often fol. by up )

Her courage was buoyed by the doctor's assurances.

to float or rise by reason of lightness.

noun

beacon , drift , float , guide , marker , signal

verb

bolster , prop , support , uphold , animate , elevate , exhilarate , flush , inspire , inspirit , lift , uplift