After Craig is pushed face first into a muddy hold by Davidson he is next seen with a dirty overcoat but his face and hair are completely spotless.
To get back down river after dealing with those that wronged him Phillip (John Mills) jumps into the deep hold of a river cargo barge of which there is no way of him physically getting out but some how he gets back on shore.
Though the latter action is set 12 years after the initial scenes none of the characters have physically aged in that time.
Regarding Boyd nor recognizing Fay after 12 years even though she had not aged... First: she did look more mature. Second: it was not clear how well they had known one another in the past, so he might not have recognized her. It was her father with whom he had the connection.
Bob Lowther and his wife are in separate beds and have been talking when he suddenly says 'Are you awake?'