What does a topmark consisting of a single green cone indicate?

A topmark consisting of a single green cone indicates that the buoy is a starboard hand mark. In the IALA Maritime Buoyage System, the starboard hand mark is used to indicate the right side of a navigational channel when approaching from seaward. This marking is essential for safe navigation, as it helps vessels understand where to steer in relation to the channel's boundaries.

The green color of the cone signifies that it is associated with the right-hand side of the channel for returning traffic, as boats approach a harbor or congested area from the sea. This type of signaling is crucial for maintaining proper course and avoiding hazards in waters where navigation buoys are employed. Understanding the significance of various topmarks is vital for mariners to follow safe navigation practices and ensure they are making the correct navigational decisions in open waters.