Question 39

The Correct Answer is D **Explanation for Option D (law enforcement vessels):** Option D is correct because the use of a rapidly flashing blue light is a specific requirement found exclusively in the U.S. **Inland Navigation Rules** (33 CFR § 83.36(b)). This light is displayed only by law enforcement vessels (Federal, State, or local) when they are engaged in direct law enforcement or public safety duties. **Explanation for Incorrect Options:** **A) dredge pipelines on trestles:** Incorrect. Dredge pipelines or associated structures usually display white or yellow lights, conforming to requirements for fixed structures or aids to navigation, but not a flashing blue light. **B) air-cushion vessels in the non-displacement mode:** Incorrect. Air-cushion vessels (like hovercraft) operating in the non-displacement mode are required to display a high-intensity, all-around flashing yellow light in addition to their standard navigation lights, as specified in Inland Rule 23(b). They do not use a flashing blue light. **C) U.S. submarines:** Incorrect. When submerged submarines are surfaced or operating on the water, they are usually identified by a high-intensity, all-around flashing amber (yellow) light, in addition to standard navigation lights, if they are involved in certain exercises or operations. They do not use a flashing blue light.