centre buoy

例句：

1. 1. The ship's centre buoy marks the exact position of the vessel.
   船只的中心浮标标明了船只的准确位置。
2. 2. The buoy was used to guide ships through the narrow channel.
   这个浮标被用来引导船只通过狭窄的航道。
3. 3. The buoy was a crucial part of the navigation system for the boat.
   这个浮标是小船导航系统的关键部分。