noun
buoy; floating marker
A floating object anchored in water to mark a location, warn of hazards, or indicate a mooring point.
See also: 浮標
港の入り口に赤いブイが浮かんでいる。
A red buoy is floating at the harbor entrance.
noun
lifebuoy; life ring
A ring-shaped or similar flotation device thrown to a person in the water to prevent drowning.
船から落ちた人にブイを投げた。
They threw a lifebuoy to the person who fell from the boat.