STOP THIS NONSENSE!
anyone can be in charge of a navigation watch if they have the required license for the vessel and it is only up to all the parties involved to decide who is in fact the person in charge. I get a meal relief and go down to eat, the relieving officer becomes in charge of the watch. There are two OICNWs on the bridge and one wants a break, the other officer can assume being in charge of the watch as long as the two parties agree and hand over the conn. The other man can leave the bridge if he so wishes but that would eliminate having a lookout present which is required by the COLREGS. Some vessel masters might require an AB be present on the bridge if one officer leaves but that is up to the master to require in standing orders. As far as I know there is no regulation in the CFRs that say that there always must be two or more men present while a vessel is underway (but I may be wrong on that). I do know that many vessels operate with only one man on the bridge in favorable conditions.
the nub of this is, if I am the OICNW and leave the bridge without another qualified OICNW present then I remain in charge of that watch and fully liable for anything that might occur when I am not present HOWEVER, if I leave the bridge with another qualified OICNW present with the clear understanding between both of us that he is now in charge, then I leave without liability for that man’s actions. ALL THAT IS REQUIRED IS THERE BE A QUALIFIED OICNW DIRECTING THE MOVEMENT OF THE VESSEL…PERIOD!