Since rule #4 was so short I thought we would go right into rule #5 Look Out.
Rule 5 - Lookout
Every vessel shall at all times maintain a proper look-out by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the situation and of the risk of collision.
Here is where it gets dicey with the pleasure boater, in essence what they are saying here is the captain is advised to appoint a second person as look out who has no other duty other than be an extra set of eyes for the captain. No attending to kids, no drop below for a beer real quick, no talking and waving to those you are traveling in company with, just watching for any danger or special circumstance you may be happening upon. The Captain is only advised to do this thus leaving an out for the pleasure boater however if there is some sort of accident/collision the Captain may held negligent for not adhering to this rule. The other piece of this "as by all available means appropriate in the prevailing conditions" means if you have a radar that is operable, you should be using it, if you have an operable depth sounder you should be using it etc. If you are in a collision in any condition with an operable radar on board and you where not using it you may be held negligent for this as well. My advise would be if there is another person topside with you while underway have them paying attention with as little distraction as possible to help you with situational awareness.
Again only advise from me, don't take my word for it, do your homework, be a responsible boater.