Story Structure — 5 Plot Phases
Friends Beneath the Water
Kim Jun and Lee Tae-hyeon grow up inseparable and volunteer for the SSU together. Training brings an injury and a dangerous accident, raising questions about responsibility and the risks imposed on divers.
Key Events
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Growing Up Together — Jun and Lee grow up inseparable, sharing a life beneath the water. Characters: Kim Jun, Lee Tae-hyeon
Location: Underwater
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Joining the SSU — Both friends volunteer for the SSU and continue serving together. Characters: Kim Jun, Lee Tae-hyeon
Location: Naval service
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Jun Explains His Choice — Jun says he joined because he could not bear separation from Lee and likes wearing the uniform. Characters: Kim Jun, Lee Tae-hyeon
Location: Naval service
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Training Altercation — A training altercation leaves one of the men injured. Characters: Kim Jun, Lee Tae-hyeon
Location: Training area
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Missile Recovery Exercise — The divers take part in an exercise to recover a missile. Characters: Kim Jun, Lee Tae-hyeon
Location: Underwater training site
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Cable Failure — A cable failure during the exercise causes an accident. Characters: Kim Jun, Lee Tae-hyeon
Location: Underwater training site
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Sergeant's Embolism — The accident gives a sergeant a dangerous gas embolism. Characters: Kim Jun, Lee Tae-hyeon
Location: Underwater training site
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Responsibility Dispute — The injury triggers a confrontation about responsibility and risks imposed on the men. Characters: Kim Jun, Lee Tae-hyeon
Location: Naval unit
A Friendship Under Strain
Years later, Jun and Lee remain in the navy, but their relationship is increasingly tense. Jun challenges Lee, while the navy develops the USM and plans Operation Mink.
Key Events
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Years Later — Years later, Jun and Lee are still serving together, but tensions have grown. Characters: Kim Jun, Lee Tae-hyeon
Location: Naval unit
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Jun Challenges Lee — Jun confronts Lee about his conduct and his relationship with their commanding officers. Characters: Kim Jun, Lee Tae-hyeon
Location: Naval unit
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USM Development — The navy develops the USM, designed to combine sonar and jamming capabilities. Characters: Kim Jun, Lee Tae-hyeon
Location: Navy
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Operation Mink Planned — The navy plans a long-duration submarine exercise aboard the Han-Ban-Do. Characters: Kim Jun, Lee Tae-hyeon
Location: Navy
The Dangerous Recovery Order
After Big Mouse is lost, the team is ordered to retrieve it and its data from 155 meters. The operation proceeds despite weather, survey, and diver-safety concerns, with Jun and Lee's conflict complicating their work.
Key Events
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Big Mouse Lost — The underwater camera known as Big Mouse is lost, prompting a recovery order. Characters: Kim Jun, Lee Tae-hyeon
Location: Underwater
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Recovery at Depth — The team is ordered to recover Big Mouse and its vital data from 155 meters. Characters: Kim Jun, Lee Tae-hyeon
Location: 155-meter depth
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Hazardous Mission Approved — The mission is approved despite weather concerns, no site survey, and danger to the divers. Characters: Kim Jun, Lee Tae-hyeon
Location: Naval unit
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Strained Teamwork — Jun and Lee's strained relationship complicates the work, though Lee believes the team can succeed. Characters: Kim Jun, Lee Tae-hyeon
Location: Salvage operation
The Submarine Emergency
The Han-Ban-Do floods, loses power, and comes to rest on a reef. Signs of life prompt a rescue effort that also aims to recover the USM and black box.
Key Events
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Submarine Flooding — The Han-Ban-Do suffers flooding and loses power. Characters: Kim Jun, Lee Tae-hyeon
Location: Han-Ban-Do
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Han-Ban-Do Grounds — The powerless submarine sinks onto a reef. Characters: Kim Jun, Lee Tae-hyeon
Location: Reef
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Signs of Survivors — The navy detects signs of life in the submarine's control room. Characters: Kim Jun, Lee Tae-hyeon
Location: Submarine control room
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Rescue Team Dispatched — A rescue team is sent to save survivors and recover the USM and black box. Characters: Kim Jun, Lee Tae-hyeon
Location: Naval rescue operation
Rescue Without Resolution
Kang speaks with Jun about their reunion and her final mission. Divers secure the rescue vehicle and prepare to extract the survivors, but the transcript ends before their fate is resolved.
Key Events
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Kang Speaks with Jun — Kang tells Jun she has reunited with him, asks him to visit afterward, and says this is her last mission. Characters: Kim Jun, Kang Su-jin
Location: Rescue operation
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Rescue Vehicle Secured — Divers secure the rescue vehicle to the submarine and confirm survivors are inside. Characters: Kim Jun, Lee Tae-hyeon, Kang Su-jin
Location: Stricken submarine
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Rescue Underway — The divers prepare to bring the survivors out; the transcript ends before their fate is known. Characters: Kim Jun, Lee Tae-hyeon, Kang Su-jin
Location: Stricken submarine