...Bottom line - while people sincerely believe they are fully functional, both mentally and physically, while catnapping, and that they are not placing themselves or others in any danger because they are in the vast expanses of the ocean, in reality this is never the case. If the boat is moving and the captain is asleep at the helm, then Houson, there is a problem..:
There is where we disagree. I recognize that I am not fully functional when sleep deprived. So what? I would prefer to be fully functional, but that is not an option. I am capable of safely cruising a boat at less than optimal functioning.
The solution: you should have safe, efficient, redundant, routine practices while underway. If you sail your boat in such a way that you continually require your utmost skills and abilities after 4 or 5 days underway, you will probably be in trouble.
Driving a car is not a fair analogy to cruising a sailboat offshore or on coastal hops. Driving a car requires much greater continuous concentration or focus than sailing a boat in the ocean. In most places, if you nod off on the highway for 20 minutes, you will be in an accident of some kind. At sea, you have just gained some beneficial rest and nothing has happened. If you are scanning the horizon when you wake and you only sleep in 20 minute increments, it is highly unlikely you will strike another vessel. In addition, as many have commented, there is really not that much vessel traffic out there, beyond the major ports (contrary to the many posts on Sailnet by the folks who plan to immediately buy a boat and sail to Hawaii or England with no prior experience).
BTW, I respect the ability of physicians to function on less than adequate sleep. I understand the profession believes that is a useful and necessary skill acquired over time through practice.