Along his branch line, Thomas often looks forward to the sight of the river, and the people that fish there. He often wants to stay and watch, but his driver will not let him, knowing that the Fat Controller would be cross if they fell behind schedule by stopping to fish. Whenever he meets another engine, he shares with them his desire to fish, but they all tell him that "engines don't go fishing," which he does not take seriously.
One day, Thomas arrives at the junction to find the water column is out of order. Thomas is thirsty, but his crew decides to get water from the river instead.
The crew finds an old bucket and rope and hurry to the bridge. Once there, they lower the bucket down to the river. Unfortunately, the bucket has five holes and the water leaks out fast, so they have to hurry and pour it into Thomas' tank before it drains out. They repeat this several times until at last Thomas' thirst is quenched.
Before long, Thomas develops a sudden pain in his boiler. Steam rushes from his safety valve, and Thomas is alarmed that he may burst. The crew dampens the fire and they struggle on to Ffarquhar. Annie and Clarabel are uncoupled and Thomas, still aching, limps onto a siding while the guard phones an inspector and the Fat Controller. Workmen put signs saying "DANGER KEEP AWAY" all around Thomas. The inspector and the Fat Controller arrive and console Thomas over the situation. The driver explains what happened, and the inspector determines that the feed pipe is blocked.
When the inspector looks inside Thomas' tank, he notices something then climbs down and asks the Fat Controller to take a look in the tank as well. The Fat Controller is shocked at what he sees; they both agree that it was fish and deduce that they were collected in the process of filling the tank. The Fat Controller jokes that Thomas got to go fishing after all, but as fish do not suit him they must be removed at once. The crewmen carefully fish them out with instructions from the Fat Controller and afterwards they have a meal of fish and chips. The Fat Controller hopes that Thomas has learned his lesson, to which Thomas replies that he now understands why engines do not go fishing; it is too uncomfortable.
- The Railway Series story of the same title, is a favourite of both Wilbert Awdry and his son Christopher.
- Stock footage from Thomas and the Trucks is used.
- This is the first episode to have the same title in both the US and the UK.
- The episode can be seen in a Japanese game, "Magical Adventure".
- This is the first episode to not be dubbed in Latin American Spanish and Brazilian Portuguese.
- In 2010, Thomas' horrified face when the Fat Controller asks the inspector if he saw fish, along with the sound effect that went with the shot, became an internet meme.
- Some of the gold paint on James' dome is faded.
- In one scene, Annie and Clarabel are facing the wrong way.
- The narrator says the bucket has five holes, but a close-up shot shows six holes on the bucket. Also, no water is seen leaking in the next two shots.
- When the bucket is lifted from the river, the water is shown to be brown and muddy. However, when the water is poured into Thomas's tank, the water appears to be clean.
- When Thomas begins to feel a pain in his boiler, he passes by the spot he ends up stopping in.
- Thick pencil marks are visible on the "DANGER KEEP AWAY" signs.
- The audio clip of the Fat Controller saying "Mmm" was placed on the M&E track instead of the dialogue track, as can be heard on some prints of the original "Volume 1" Guild Home Video release. As a result, the George Carlin narration and all international versions have this audio clip in the background.
- When the men are first seen with the "DANGER" signs, the red lining around Thomas' number is peeling away.
- The narrator says they put the signs in front and behind Thomas, but in one shot of Thomas, a sign that is supposed to be behind him is on the right side (viewer's perspective) of him.
- When the Fat Controller and the inspector are looking in Thomas' tank, the light pole behind Thomas is missing.
- In the restored version, studio equipment can be seen when Thomas says "Bother! I'm thirsty!" and when the inspector looks inside Thomas' tank.
- When Thomas puffs on to the siding, steam continues to vent from the tracks even after he leaves, but in the next shot, it all disappears. Later, when the inspector clambers up to check Thomas' tanks, Thomas abruptly stops hissing steam, but when the inspector comes down, he is hissing steam again and once the Fat Controller climbs up, the steam vanishes. Then, when the Fat Controller asks Thomas' driver how the fish got there, the steam reappears. Throughout all of this, the hissing sound continues even when Thomas is not letting off steam.
- When Thomas is at Elsbridge, the siding usually seen at the water column is not there, except in the close-up of the out of order sign. When it is seen, it ends in the grass.
- There is a tiny hole in Thomas' smokebox when the Inspector looks into his tank.
- When the bucket is pulled in and out of the water, the string attached to it leading into Thomas' cab is visible.
- Thomas is wearing Percy's tired face mask in four shots.
- In the Welsh narration, only one of the "DANGER KEEP AWAY" signs is translated into Welsh, while the others remain printed in English.