A ferry crossing already has a structure: the loosening from shore, the stretch of water, the return to a line of buildings that grows steadily less abstract. Three tracks can be enough to accompany it.
Begin with something that leaves space. The first minutes may include an announcement or instructions you need to hear, and the changing view deserves attention of its own. A track with a patient opening can meet the journey without trying to direct it.
In the middle, choose the piece you most want to spend time with. It might have a long instrumental passage or a rhythm that makes the movement of the boat feel newly apparent. Keep the volume low enough to remain aware of what is happening around you.
The last track is optional. As the shore approaches, there are bags to collect and routes to work out. Stopping the music before it resolves can be preferable to missing information because you wanted a perfect ending.
You could make the crossing with no playlist at all and lose nothing. The useful idea is the small scale: select a little music for a little time. When every available minute has been filled in advance, there is less room for the journey to surprise you.
