Alternatively he could be delivering to Bit and then moving on to investigate why trade has slowed to a halt further in land up the river if that's easier to write in?
Welcome to pbp, I too am newish. And that hook will probably work best. No trade making it to port will make a dwarf wish to investigate.
Question - Are you taking the Ship's Passage as your background trait? I think it would be very helpful in later adventures shoudl we wish to travel.
And again welcome.