Me Myself:
As to merchant navy, the man power is exactly the same as on an aircraft : one captain, one first mate and a second mate who gets the worst shift, middle of the nigh most of the time. Same down in the engine room.
Apart from none of that being correct for major oceangoing vessels, ships stays at sea up to 30 days or more at the time. Not really a relevant comparison with aviation wich counts their airtime in hours.
Per