In clear weather, what should a vessel at anchor sound when another vessel approaches on a steady bearing?

When a vessel is at anchor and another vessel approaches on a steady bearing, it is necessary to indicate its presence to avoid a potential collision. The appropriate sound signal in this situation is five or more short and rapid blasts on the whistle. This signal is used to communicate that the vessel at anchor is unsure of the intentions of the approaching vessel and is alerting them to its presence.

This rule is established in the COLREGs (International Regulations for Preventing Collisions at Sea), which dictate sound signals for various situations to enhance safety at sea. The use of five or more short blasts serves as a warning to the other vessel, as it may not be clear whether the approaching vessel has seen the anchored vessel, particularly if visibility is good.

The other options suggest different sound signals that are either inappropriate or not applicable in the context of a vessel that is anchored.