What color is used for a navigational marker indicating the left side of a channel when returning from the sea?

The correct answer is red, which is used for navigational markers indicating the left side of a channel when returning from the sea. This is part of the IALA (International Association of Lighthouse Authorities) buoyage system, which establishes maritime navigation standards.

In this system, red buoys or markers are typically referred to as "can buoys." They are designed to aid mariners by providing clear guidance and helping them navigate safely when entering a channel. When returning from open waters, vessels should keep the red markers on their left side, a practice often remembered through the phrase “red-right-return.”

Other colors like green, blue, and yellow are used for different purposes in navigation. Green, for instance, indicates the right side of the channel when returning from the sea. Blue markers are generally not used for channel marking but may indicate other navigational features. Yellow might denote special markers that provide information to boaters about certain regulations or hazards. Understanding these color codes is crucial for safe navigation on waterways.