Looking for opinions on the best option(s) for swapping watches mid-hitch.
Scenario: Mariner A arrives at vessel for midnight crew change, having been up all day. Goes to bed, gets up for noon-midnight. Stays on noon-midnight for two weeks +/-, then switches to midnight-noon for the last two weeks. Mariner A is rested and ready for his first watch, and rested and ready for a long, overnight drive home at crew change. Mariner B, meanwhile is on midnight-noon for his second two weeks, and is rested for his drive home. Mariner C arrives at Mariner A’s two week mark for midnight crew change, and needs to get some rest before standing watch.
How do we most fairly and safely get Mariner A onto the midnight-noon?
Is an 18-hour watch for each man the only, or best, option? Spread it out over a couple of days?
Have I made this more difficult than it needs to be? Primary issue is crew rest for vessel operations and for travel. Secondary issue is that each mariner has a fair shot at working days/nights with all that entails.
Feel free to use small words and/or pictures and diagrams. <not good at math>