Question 39 RVR04 - Master or Mate of LT 200 GRT

The Correct Answer is D A flashing blue light, when used **INLAND ONLY**, is specifically prescribed in the Inland Navigation Rules as an identification light for **law enforcement vessels** when they are engaged in enforcement duties. Rule 21(e) of the Inland Rules governs the use of this light, stating that "A vessel engaged in law enforcement activities may display a flashing blue light when in operation." Here is why the other options are incorrect: * **A) dredge pipelines on trestles:** Dredge pipelines, including those on trestles, are usually marked by fixed yellow or white lights, depending on their location and extent, but not a flashing blue light. They are considered obstructions/structures, not vessels requiring the blue identification light. * **B) air-cushion vessels in the non-displacement mode:** Air-cushion vessels (ACV) operating in the non-displacement mode (flying/hovering) display an all-round flashing **yellow** light to indicate that they are subject to special operational rules (Rule 23(b) and Annex I, 9(e) of the Inland Rules). They do not use a flashing blue light. * **C) U.S. submarines:** While U.S. submarines have specific, unique lighting requirements when surfaced (Rule 24(f) and special notices), these typically involve a flashing **amber/yellow** light, not a flashing blue light. The flashing blue light is reserved for law enforcement.