If an anchored vessel is greater than 50 meters, what must it show?

An anchored vessel that is greater than 50 meters in length is required to show a second all-around light. This requirement is in accordance with the COLREGs, specifically Rule 30, which addresses the signaling of anchored vessels. The two all-around lights are typically displayed in a vertical line with the upper light being white. This enhances visibility and indicates to other vessels that the anchored vessel is indeed secure and at anchor, thus reducing the risk of collision.

In contrast, the other options do not fulfill the requirements set by the COLREGs for anchored vessels of this size. A single all-around light would be insufficient for larger vessels, and flashing lights or sound signals are not mandated under this specific scenario for anchoring. The intent of these regulations is to ensure navigational safety and proper identification of vessels in various situations.