Rule 7

Risk of collision

Any visibility

Use all available means to decide if risk exists — a steady compass bearing on a closing vessel means it does.

In plain language

The classic test: take repeated compass bearings of an approaching vessel. If the bearing does not appreciably change while the range closes, you are on a collision course — constant bearing, decreasing range. Use everything you have (eyes, radar, plotting), never judge from scanty information, and if you are in any doubt, the rule decides for you: assume the risk exists. Beware — a slowly changing bearing can still mean risk with a very large ship or a tow.

Takeaway

Steady bearing + closing range = collision course. If in doubt, assume risk exists.

Easily confused with

Rule 8 — Action to avoid collision
Rule 7 tells you how to decide risk exists; Rule 8 tells you how to act on it — early, substantial, and checked until past and clear.