Bigg Freeze is the thirteenth and final episode of Tugs.
Winter has arrived, and nothing is able to come in or out of Bigg City Port. However, the tugs are expecting the S.S. Vienna to arrive, so Hercules is given the task to bring the cruise liner in as far as Lillie Lightship. Lillie is low on fuel, and asks Hercules if he had seen Ten Cents, which he hasn't yet. Hercules warns Lillie that if she is unable to guide her in with her light, Vienna would sail on to the next available port.
Meanwhile, Ten Cents and Sunshine are trying their best to find a fuel barge for Lillie Lightship. Captain Star has told them that, if Lillie's light is not working when S.S Vienna arrives, the cruise liner will not risk running-aground and so it will sail on to the next port, meaning it is vital that they find a fuel barge quickly. The two switchers know that the whole operation depends on them. Unfortunately, the only fuel barge they find is in the tow of Zorran. They try to convince Zorran to give them his fuel barge so they can supply Lillie Lightship. However, Zorran refuses, believing that Ten Cents and Sunshine are going to supply Vienna's heating plant, which is his job.
Ten Cents and Sunshine tell O.J. about Zorran and the fuel barge, and O.J. agrees that Zorran is making a big mistake; without Lillie's light, there will be no visit from Vienna for either fleet. Just then, Sunshine has an idea and suggests to collect the emergency light barge, which is stored up at the creek. O.J. agrees and tells the Star switchers to collect it as quickly as they can before dark. The Zero switchers, Zip and Zug, had eavesdropped on the conversation, and they mistakenly thought that Ten Cents and Sunshine were going to collect another fuel barge and try to beat Zorran to Vienna.
Meanwhile, at the garbage dump, Warrior is struggling to find an empty barge as Lord Stinker is full and no full barge can be unloaded because Jack is out of action due to the freeze up. Fortunately, he finds a reasonably suitable one and exclaims to Lord Stinker, "There is one over there, half-full... I mean, half-empty!"
At the creek, Ten Cents and Sunshine find the emergency light barge; but Zip and Zug, having overheard the conversation earlier, use a moored fire barge and jam it across the creek, trapping the Star switchers inside. Despite their best effort, Ten Cents and Sunshine cannot move it until Sunshine explains about the night tide (another part of the creek is low tide during the day and high tide during the night) and it leads back to the river.
Night falls, and Zebedee, Zak, Big Mac, O.J. and Top Hat are waiting for Vienna. When Warrior arrives, O.J. is concerned as Ten Cents and Sunshine have not arrived yet. So, they all suggest how to make Hercules and Vienna know where they are. No one has an idea until Warrior suggests to burn the garbage in his half full/half empty barge, which will make a beacon light. Warrior's plan works until the fire burns out, but luckily, Ten Cents and Sunshine arrive with the emergency light barge, and with a bit of accidental help from Warrior, the light barge is turned on. Now, Hercules and Vienna are able to continue on course for the bay under bright guidance.
Just after Zorran arrives, Zip and Zug turn up, and they are very surprised to see Ten Cents and Sunshine there. Zorran asks Zip and Zug what they were trying to explain to him at the fuel depot, so Zip tells Zorran that they blocked the Star switchers with the fire barge, so that the fuel still stayed with Zorran. But when Ten Cents explains about the emergency light barge, Zorran realizes why the Star switchers wanted the fuel barge, and scolds Zip and Zug for being so stupid. The irony being that Zorran being so selfish with the fuel barge earlier would have lead to Vienna sailing on to the next port inevitably, anyway. Quickly, Zip and Zug leave to clear away the fire barge before the Fire Chief turns up.
Soon, Hercules arrives with Vienna and both the Z-Stacks and the Star Tugs set to work to load and unload their barges. However, Vienna has enough fuel to get to the next port, and she does not need to take on anymore, so Zorran decides to give his fuel to Lillie Lightship.
In the end, Zip and Zug get into deep trouble with the Fire Tug and Lillie is happy to have her light on again. The S.S. Vienna continues onwards with her voyage by singing a farewell song to the tugs and with the echoes of Top Hat, Ten Cents, and Sunshine saying, "Goodnight, Vienna!"
- Ten Cents
- Big Mac
- Top Hat
- Fire Tug
- S.S. Vienna
- Lillie Lightship
- Lord Stinker
- The Fuel Depot Manager
- Captain Star (narration only)
- Jack (cameo)
- Zebedee (cameo)
- Zak (cameo)
- Izzy Gomez (deleted scene; cameo)
- Captain Zero (mentioned)
- The song in this episode is sung by Sue Glover of Sunny and Sue fame as S.S. Vienna.
- This episode marks the only appearance of the Fuel Depot Manager.
- This episode marks the final appearances of the Star Tugs, the Z-Stacks, Lillie Lightship, Fire Tug, Jack, S.S. Vienna, the shrimpers, Izzy Gomez, and Lord Stinker.
- Stock footage from "Ghosts" and "Regatta" is used.
- The picture book adaption of this episode is retitled Bigg City Freeze.
- The Japanese title translates to The Day the Harbour Froze.
- When Ten Cents and Sunshine search for a fuel barge, O.J. constantly changes his position on the river.
- The song at the end of the Japanese dub is the original English version.
- Because stock footage from "Regatta" is used, Lillie's light is not covered in ice in a closeup.
- When Ten Cents asks, "What's going on?!" steam suddenly appears beside him, indicating a film cut.
- In one of the picture book adaptation's pictures, Sunshine has a loose fender.