noun / verb
buoy
BOO-ee/ˈbuːi/
A floating object used to mark a place in water.
A red buoy marks the edge of the shipping channel.

Etymology
The origin is disputed: a possible connection with “beacon” fits its signaling role, while a proposed link with “fetter, chain” refers to its being anchored to one spot.
In context
When you see a buoy with black and white stripes that means there's an obstruction running from that buoy in toward shore, so make sure you go all the way around it.
More examples
- The life jacket buoyed him until help arrived.
- Her encouraging message buoyed my spirits.
- A new grant buoyed the struggling research program.
Forms
buoy · buoys · buoyed · buoying
buoyant adjective — Able to float or remain cheerful and hopeful.
Similar words
- float
- Anything that stays on the surface, while a buoy commonly marks a location.