Lets say you are the Master onboard an OSV in the GOM and when crew change comes around you and your crew are flying out. But the rig will not have the Helicopter shut down so they can send your relief down let you do your turn over and then pick you up (they can’t operate the cranes with a Helicopter running on deck). What they want it’s to pick you up before the Helicopter arrives have you do the turn over (if any) in the rig then have you fly out and when the Helicopter is gone send your relief down to the boat.
So the vessel is without a master alongside a platform on DP. This evolution could take anywhere between 45 min to 3 hours.