Audio problem: When Arthur arrives at the lake, he has Spencer's whistle.
Continuity mistake: Because of the production order, Murdoch appears at the sheds, but his introduction is 2 episodes later, in "Peace and Quiet." Spencer also appears at the sheds, but his introduction is 8 episodes later, in "Gordon and Spencer."
Visible crew/equipment: When Thomas says "But I'll be much better when you take these fish away!", a tripod is reflected in the water. (HD widescreen only).
Continuity mistake: Thomas was pushing 4 trucks and a brake van, but when the trucks are laughing at Thomas, there are 2 trucks and a brake van. A truck also gains a face.
Continuity mistake: The fisherman appears out of nowhere when he tells Thomas to enjoy the smell of the fish.
Continuity mistake: When Arthur is waiting for the fat controller to pick him to run the new line, in a wide shot of the sheds, Henry is very close to him, but in a close up of Aurthur, Henry has vanished and Gordon appears one line beside him.
Visible crew/equipment: When Arthur arrives at a station, a shadow of studio equipment is visible on the left.
Answer: He was in the water.