Lights on the port bow
A fishing vessel at night. Advanced level, about 3 min. COLREGs Rules 18 & 26.
The situation
It is night. On your port bow you see a green all-round light above a white one, and below them a green sidelight. The bearing is steady and the range is closing. You are under power.
Who keeps out of the way?
- Slow down and let her cross ahead: Keep out of the way of the fishing vessel.
- Stand on: she is on your port side: Apply the crossing rule.
- Turn to port to pass astern of her: Cross behind her trawl.
Lookout: Read the lights before applying the crossing rule. Green over white is a vessel engaged in trawling, and her green sidelight shows you are on her starboard side.
The sound answer
Slow down and let her cross ahead
Green over white is a vessel engaged in trawling. Under Rule 18(a)(iii) a power-driven vessel underway keeps out of the way of a vessel engaged in fishing, even though she is on your port side. Slowing to let her cross ahead is the authored example.
Why the other options fall short
Stand on: she is on your port side
Rule 15 applies between two power-driven vessels. A vessel engaged in fishing is not treated as an ordinary power-driven vessel; Rule 18 makes you keep out of her way.
Turn to port to pass astern of her
Turning toward her takes you close astern of a trawler, which is exactly where her gear is towed. Keeping out of the way means leaving her and her gear well clear, as slowing does here.
Rules 18 & 26 · Fishing vessels
A power-driven vessel underway keeps out of the way of a vessel engaged in fishing. A vessel trawling shows two all-round lights in a vertical line, green over white, and when making way her sidelights and sternlight.