"City Under the Sea" is the fourth episode of the second season of Thunderbirds Are Go!, and was broadcast on the 5th November, 2016.


The Sullivan family, on holiday in the flooded Bay City, veer off the tour area and come face to face with the Mechanic, who is tearing apart Creighton-Ward building. The Mechanic is looking for the plans to Parkmoor Scrubs prison, so he can free the Hood, but the debris from the crumbling building hits the Sullivan's sub and they crash to the bottom of the sea. Gordon and Kayo are sent out to rescue them, but things get tense when the Mechanic attempts to destroy another one of their machines. Lady Penelope, with Parker as chauffeur, uses her knowledge of the building to locate the plans first, but can they escape before the Mechanic notices?


Regular CastEdit

Guest CastEdit

International Rescue Equipment Used Edit

Non International Rescue Equipment Used Edit




  • The TX-204 safe is a reference to the TX-204 target carrying aircraft from Trapped in the Sky.
  • Unlike Chain Of Command, when Kayo boards Thunderbird 2 with Gordon, she has more animation than Alan and Scott when they entered the craft.
  • Even though this is Kayo's first time in Thunderbird 4, she is able to control the craft. She is seen earlier in the episode to be watching what Gordon is doing while he is in the pilot's seat, making the assumption that she can learn skills on the fly.
  • This is the first time fish can be seen swimming in the water of the ocean.
  • Magna Prime can be seen attached to the Crab Ship.

Goofs Edit