It is the 1920's: Rival tug fleets compete for work in Bigg City Port. Captain Star briefs his Star Tugs - he's trying the regular contract to dock The Duchess ocean liner. It'll be a difficult job but to help out, the captain has recruited Sunshine, a small switcher. The rival Z-Stacks are encouraged by their devious Captain Zero to sabotage the operation. Their leader Zorran runs Big Mac aground, and nudges Sunshine into The Duchess's bow, swinging her dangerously. Captain Star orders Sunshine's dismissal, but he runs away, and is lost in the harbour in a thick fog.

Ten Cents delivers his last cargo barge to the Old Quay after a very busy day. As night falls, it is towed away by a mysterious boat. Captain Star is cross to hear that one of his customer's deliveries is missing and puts Ten Cents on dredger detail - not a pleasant task. But Grampus, a small submarine, sees another barge being stolen at night, so Captain Star and Captain Zero join forces to find the thief....

The Z-Stacks must share the up-river jobs with the Star Tugs. When a tramper that Zorran and Zug are towing goes out of control blocking the river and trapping the Stars, Zorran tries to take advantage of the situation to get more work for the Z-Stacks. However, Zorran's scheme does not go as he planned.

Lillie Lightship is sad. Moored out of the harbour to guide boats and keep them out of danger, she never gets to see the Regatta. In spite of Lillie's warnings, a tramper sees her too late and hits her, making a large hole in her side. The Star tugs rescue her and she is towed into the yard to be mended, from where she sees the exciting, colourful regatta parade, with barges decorated by dockland firms, cranes, and buildings festooned with banners.

During the annual manoeuvers, both Bigg City tug fleets service the navy. It is a dangerous job, handling ammunition and explosive barges. All is going smoothly until Bluenose, a bossy naval boat demands immediate priority with a barge-load of gasoline barrels. OJ, the oldest of the Star Tug fleet, warns that it's dangerous to stop the operation half-way through, but Bluenose insists and pushes in roughly. The movement knocks barrels of gasoline off the barge and they split open, spilling their dangerous contents. A spark from Bluenose's stack starts a series of fires and explosions which puts all the tugs in great danger.

Warrior had always had a reputation for being a bit clumsy, but on this day he sets out to prove to Captain Star that he is capable of working without causing accidents. However, on his usual trips between the quarry and the old quayside he is as clumsy as ever and is told to report to Captain Star to answer to the many complaints about the damage he has caused. On his way to see Captain Star, he hears that Ten Cents is in danger, so he goes to help him straight away. The day has been a disaster so far but will it end that way?

The Stars and the Z-Stacks are both competing for a big steel contract. the fleet which can transport the most steel in one day, wins the contract. The canal is a short cut through Bigg City but Big Mac of the Stars decides to go round the bay and let Zebedee and Zak of the Z-Stacks take the short cut through the canal. At first Warrior of the Stars is confused by Big Mac's idea for both of them to go round the bay, but as you'll see the short cut through the canal wasn't necessarily the best route.

It has been one of the hottest weeks of the summer. In such hot weather, there was a greater danger that ships might be carrying diseases. If this was the case, the ships would have to go into quarantine for several days and wait out in the estuary, away from the harbour. Under no circumstances should any of the tugs go near the ships in quarantine. Ships in quarantine fly the yellow flag. When the old tramper, Nantucket, lowers its flag, a great deal of confusion is caused and only wise old O.J. understands why.

Old sea stories - especially about ghosts - are favourites amongst the tugs of Bigg City Harbour. No one will admit to taking them too seriously; so when Big Mac rushes back to the Star Pier one foggy night the other tugs laugh when he tells them he actually saw the "Ghost Fleet" looking for lost tows. However, mysterious things happen the very next night that make the Star Tugs uncertain as to whether the Ghost story is true or not.

An old dirty tramper from Australia suspected of smuggling lurks outside the limits of Bigg City bay. It is the notorious Johnny Cuba. When bad weather suddenly comes, he forces Zebedee, one of the Z-Stacks, to tow him into the safety if the harbour and into hiding. Normally, Zebedee would have been glad to help out an old friend but this time - things are different.

Towing huge piles of logs was always a very dangerous operation. When the snows began to melt and the rivers swelled it added to the danger. Because of the sudden rush of water that it could cause, log jams had to be carefully untangled. One day, a particularly nasty log jam had occurred and Big Mac was being helped by Sunshine to try and clear it. Before Big Mac could stop him, Sunshine rammed into the high log jam and found himself trapped. Ten Cents arrives to help Big Mac free Sunshine, but one false move could spell disaster.

An Ocean liner called Vienna is to come into Bigg City Port but Lillie Lightships needs to refuel, if there isn't a light Vienna can't come. Supplies are low, Ten Cents and Sunshine try to find oil for Lillie but they only find one which Zorran has and he won't give it to them, He says it's for Vienna. Sunshine knows where to find a light barge. Zip and Zug get the wrong end of the stick and trap Ten Cents and Sunshine by using a fire barge.

Both fleets are waiting anxiously for Vienna but there is no light. Luckily Warrior saves the day by setting his garbage barge alight for a light for Vienna. Ten Cents and Sunshine wait for the tide to set them free. Vienna comes to Bigg City, the tugs do their job and she goes on her way.