How can there be a 30 minute difference on the same route?
Is the train going faster? Is it skipping something?
This just occurred to me. Is it possible that the 8:10 and 12:40 tours meet somewhere on the ship, whereas the 4:30 departure meets at the train depot near/on the pier? That could account for some of the time difference as meeting off-ship eliminates the wait for tours to be called and the wait to get off the ship. Just a thought...