Common sense or "might is right"?

Remembered from New Year's Eve 2013. 

A large cruise ship (330 m long, 9 m draft, 15 decks, 10 pools, 17 bars and lounges, 4500PAX - you get the picture)  is leaving Patong Bay in Thailand. She is in probably 25-30m of water and the bay is 3 miles wide, giving to open sea. She is travelling at slow speed - considerably less than her cruising speed of 22 knots.

A small, probably 10 m, power boat is approaching from the cruise ship's starboard side.

When the power boat is  about a quarter mile off the ship gives 5 blasts on her siren, indicating that the watchkeepers were unsure of the other vessel's intentions. In such circumstances the signal is usually interpreted by small boat operators as "get out of my way".

The power boat skipper calls up on VHF radio stating "I have you on my port side. I believe that I have the right of way".

The response from the ship is "You are less than 20 metres - you have to give way. Read the Collision Regulations".

The power boat makes a rapid course alteration, as common sense says should have happened.

However, it is interesting to speculate which of the collision regulations were felt by the cruise ship officer to give his ship the right of way.

Rule 15: Crossing situations.
When two power-driven vessel are crossing so as to involve risk of collision, the vessel which has the other on her starboard side shall keep out of the way and shall, if the circumstances of the case admit, avoid crossing ahead of the other vessel.

The cruise ship is the give-way vessel.

Rule 9b: A vessel of less than 20 metres in length or a sailing vessel shall not impede the passage of a vessel which can safely navigate only within a narrow channel or fairway .

The entrance to the bay is wide and deep by reference to the cruise ship's draft. Not applicable? 

Rule 10j:  A vessel of less than 20m in length or a sailing vessel shall not impede the safe passage of a power-driven vessel following a traffic lane.

There is no traffic separation scheme. Not applicable

Rule 8f (iii): A vessel, the passage of which is not to be impeded remains fully obliged to comply with the Rules of this part when the two vessels are approaching one another so as to involve risk of collision.

Might is right!  In fact it was probably too late for the cruise ship  to take any effective action.