Question 39 RVR01 - Master of Unlimited Tonnage

The Correct Answer is D. **Why option D ("law enforcement vessels") is correct:** According to the U.S. Inland Navigation Rules (specifically 33 CFR § 84.24), a flashing blue light is a specific signal authorized for identifying law enforcement vessels while they are performing their official duties. This rule applies **INLAND ONLY**. **Why the other options are incorrect:** * **A) dredge pipelines on trestles:** Dredge pipelines, including those on trestles, are typically marked by fixed or flashing white/red lights (depending on local regulations and whether the pipeline is obstructing a navigable channel), but they are not identified by a flashing blue light. * **B) air-cushion vessels in the non-displacement mode:** Air-cushion vessels (like hovercraft) operating in the non-displacement mode must exhibit an all-around flashing yellow light (when operating on the Western Rivers or certain other specific waters, as permitted by Rule 23(b) and Annex V). They are not identified by a flashing blue light. * **C) U.S. submarines:** U.S. submarines may display an intermittent flashing amber/yellow light when surfaced and underway to indicate that they are submerged and surfacing, or when operating on the surface, but they are not identified by a flashing blue light. Their primary markings follow standard rules for power-driven vessels, supplemented by the specialized amber light.