Originally Posted by pgp
I had some vague notion of a rule set based on the traffic light. If port is red and starboard is green, you just look at the boat you're approaching and stop or go. Mentally extending the bows to a potential point of impact would quickly determine who has right of way.
Your analogy is flawed. Here is one that is more apt.

Imagine that you are driving in the right lane of a multi-lane road (in the US). There is another car behind you driving in the left lane. You approach a cross street and decide that you want to turn left. Your legal options are to change lanes, slow down (allowing the other car time to avoid you), and turn; or to slow down, let the other car pass, and then change lanes and turn. Instead, you enter the intersection and turn left in front of the other car. It brakes and swerves but still hits you in the rear quarter. Now, ask yourself who was at fault:
  1. You, because you turned in front of the other car, or
  2. him, because he should have anticipated your turn and slowed down to avoid you before you even reached the intersection?