Here is a breakdown of Rule #15 - Crossing Situation and what it means
Note that Rule #15 applies only:
- to two boats, not three or more;
- to power-driven vessels (not to boats sailing, fishing, not-under-command, or restricted in their ability to maneuver);
- in crossing (not head-on or overtaking) situations;
- after risk of collision has been determined to exist.
Before risk of collision can be established, either boat is free to maneuver at will. Once risk of collision has been established, however, the boat with the other vessel approaching on her starboard side:
- becomes the give-way vessel
- must not cross ahead of the stand-on boat unless circumstances require it.
Remember that a boat approaching on your starboard side sees your green (go) navigational light while a boat approaching on your port side sees your red (stop) navigation light.
Before crossing a narrow channel or fairway, remember rule #9, "A vessel shall not cross a narrow channel or fairway if such crossing impedes the passage of a vessel which can only navigate safey only within such channel or fairway.
Similarly, when you are in a traffic seperation scheme, Rule #10 states, "A vessel of less than 20 meters in length... shall not impede the safe passage of a power-driven vessel following a traffic lane"
A power boat underway, but not making way through the water, has no special rights. So in the event that she is approached by another power-driven vessel from dead ahead to 22.5 degrees abaft her starboard beam, then she is required by the rules to get some way on and get out of the way!