Question 19 OSV01 - Master/Chief Mate - Offshore Supply Vessels

The Correct Answer is A. **Why option A ("A vessel is on your starboard quarter, range decreasing, bearing is constant.") is correct:** The fundamental rule for determining collision risk (as defined in Rule 7 of the COLREGs/International Regulations for Preventing Collisions at Sea) is that risk exists if the Compass Bearing of an approaching vessel does not appreciably change. If the bearing remains constant and the range (distance) is decreasing, it means that the two vessels are proceeding toward the same point in space. Even though the vessel is approaching from the quarter (behind the beam), if the bearing is constant and the range is decreasing, a collision or dangerous close-quarters situation will definitely occur unless action is taken. **Why the other options are incorrect:** * **B) A vessel is 22 degrees abaft your port beam, range increasing, bearing is constant.** Although the bearing is constant, the **range is increasing**. This means the vessel is moving away from you (or at least moving away from the point of intersection), so there is no risk of collision. * **C) A vessel is broad on your starboard beam, range decreasing, bearing changing rapidly to the right.** Since the **bearing is changing rapidly**, the vessel is passing well clear ahead or astern of you, despite the decreasing range. A rapid change in bearing indicates no risk of collision. * **D) A vessel is 22 degrees on your port bow, range increasing, bearing changing slightly to the right.** Since the **range is increasing** (meaning the vessel is moving further away) and the bearing is changing, there is no risk of collision.