A visual aid, colored green, marks the port (left) side of a channel or waterway when a vessel is approaching from the open sea or traveling upstream. These markers are typically cylindrical, or can-shaped, and often carry an odd number. They are strategically placed to guide mariners safely through navigable waters. For instance, a captain returning from an ocean voyage will observe these markers on their port side as they navigate into a harbor.
The consistent color and numbering system facilitates safe navigation and minimizes the risk of grounding or collision. Historically, these aids to navigation have evolved from simple, unlit structures to sophisticated, electronically monitored devices. Their placement is critical for maintaining efficient maritime transportation routes, supporting international trade, and safeguarding marine environments by preventing accidents.
