boat train

noun1

1. •
   (UK, Ireland) A travel service with a train timed to arrive at a ferry port in time for the onward travel by ferry (or vice versa). Alternatively, a service scheduled to connect with the arrival or departure of an ocean liner.

   • With extra traffic, numerous boat trains to and from Southampton Docks, and working of empty stock, his job, like that of most signalmen, is no sinecure. — 1954