lock-keeper 
noun
A person who is employed to attend and maintain a lock on a river or canal.There are lock-keepers, vets and people we meet in bars - I am an old tart, I'll chat to anyone....
- When the ship sought to leave the port of Liverpool, tugmen and lock-keepers refused to assist its free passage.
- But Davey's quiet life changes when he falls in love with the tactless but vulnerable Sarah, a Scottish bargee who stays with him in his lock-keeper's cottage while her narrow-boat's broken propeller-shaft is repaired.