In restricted visibility, a power-driven vessel under way gives which sound signal every 2 minutes?

In restricted visibility, a power-driven vessel that is under way signals its presence by sounding one prolonged blast every 2 minutes. This practice is established by maritime navigation rules to communicate the vessel's presence and intent to other nearby vessels in conditions where visibility is limited, such as in fog, heavy rain, or darkness.

The prolonged blast serves as a warning signal to other vessels, indicating that the power-driven vessel is making way through the water. It is crucial for safety and navigation, allowing other mariners to be aware of potentially nearby vessels, reducing the risk of collisions.

The other sound signals, such as two short blasts or one short blast, are used in different scenarios. For example, two short blasts typically indicate the vessel's intention to pass another on its port side, while one short blast indicates a turn to starboard. However, these do not apply to the situation of a vessel under way in restricted visibility, where the prolonged blast is the appropriate signal to use.