Behind the Scenes of ‘The Blue Sea’: OST Gems & Secrets

When “The Blue Sea” first aired, viewers fell for its blend of romance, mystery, and a splash of fantasy. Yet beyond the on‑screen chemistry, two layers often slip under the radar: the soundtrack that underscores every emotional beat, and the behind‑the‑scenes (BTS) moments that reveal how the series came together. This article dives into both, giving you a peek at the songs that linger in the mind and the production quirks that shaped the drama’s signature look.

Why the OST matters: setting mood in a marine‑themed romance

The original soundtrack (OST) of “The Blue Sea” functions like an invisible character. Each ballad swells as the mermaid‑turned‑human (played by Jun Ji‑Hyun) discovers love, while pulsing electronic tracks accompany the investigative twists. By pairing lyrical melancholy with upbeat pop, the music mirrors the series’ tonal shifts—from wistful longing to high‑octane chase scenes.

Fans often cite “Blue Moon” (sung by Baek Ji‑young) as the emotional anchor, because its gentle piano line mirrors the film’s watery motifs. Meanwhile, “Ocean’s Whisper,” an instrumental piece crafted by composer Park Se‑joon, layers synth textures that feel like waves rolling beneath a moonlit shore. Together, these tracks give the narrative a sonic depth that viewers might not consciously notice, but certainly feel.

The standout tracks and the artists behind them

• “Blue Moon” – Baek Ji‑young: A lyrical ballad released as the series’ lead single, it peaked within the top ten on Korean digital charts and earned a nomination for Best OST at the 2020 Baeksang Awards.
• “Ocean’s Whisper” – Park Se‑joon (instrumental): This orchestral‑electronic hybrid underscores pivotal flash‑back moments, weaving strings with subtle sea‑foam sound effects.
• “Shallow Waters” – Heize: A mid‑tempo pop track that plays during the protagonists’ first meeting, its catchy chorus helped it trend on streaming platforms for weeks.
• “Tide” – Lee Hi: A soulful duet that appears in the finale, capturing the bittersweet resolution of the mermaid’s journey.
• “Current” – Kwon Jin‑ah: A lesser‑known but fan‑favorite track, used in behind‑the‑scenes videos to illustrate the production’s on‑set energy.

Most of these songs were recorded in studios located in Seoul, where the producers emphasized live vocal takes to preserve the raw emotion that the drama demands. In interviews, Baek Ji‑young mentioned she listened to ocean recordings while laying down her vocals, aiming to capture the “sound of longing that only a sea can echo.”

How the BTS footage reshapes our understanding of the drama

Behind‑the‑scenes (BTS) material released by the network showcases everything from set construction to actor rehearsals. One recurring theme is the meticulous design of the underwater set, built in a massive water tank at CJ ENM’s studio complex. The crew used a combination of practical props—like translucent acrylic shells for the mermaid’s tail—and CGI overlays to create realistic ripple effects. Director Lee Eung‑bok explained that the tank was flooded to a depth of 2.5 meters, allowing actors to practice movements that would later be enhanced with digital fins.

Another fascinating secret lies in the chemistry between Jun Ji‑hyun and Lee Min‑ho. Their initial read‑throughs were filmed for internal review, and the footage revealed a spontaneous improvisation where Jun Ji‑hyun slipped a sea‑shell into her pocket—a small prop that later became a recurring motif in the series. This unplanned detail was kept because fans responded positively during early screenings.

Production challenges: balancing myth and modernity

Adapting a mythic sea‑folk tale for contemporary television required a delicate balance. The writers consulted marine biologists to avoid glaring scientific inaccuracies, while still preserving the magical realism central to the story. For instance, the “blue‑scale” transformation sequence was choreographed with a professional swimmer, who performed synchronized movements that were later blended with CGI scales. The result was a sequence that feels both believable and fantastical.

Costume design also presented hurdles. The mermaid’s tail had to be both flexible for underwater shooting and visually stunning for close‑up shots. The design team experimented with silicone, latex, and even 3‑D printed segments before settling on a hybrid material that mimicked real fish scales while allowing quick changes between takes.

Fan‑generated content and its impact on the series

After the series aired, fan‑made videos that paired scenes with alternate music selections went viral on platforms like TikTok. Interestingly, the producers acknowledged this trend by releasing a “Fan Remix” EP, featuring reinterpretations of “Blue Moon” by indie musicians. This move not only extended the series’ lifespan but also demonstrated how audience interaction can shape ancillary content.

Moreover, the BTS clips themselves sparked a wave of “making‑of” challenges, where aspiring cinematographers tried to recreate the underwater lighting using affordable equipment. The official Instagram account highlighted a few of these fan attempts, reinforcing a community around the drama’s visual aesthetic.

FAQ

What inspired the soundtrack’s oceanic themes?

The composers drew directly from natural sea recordings—waves crashing, distant whale calls—and layered these with traditional Korean instruments to evoke both the mystery of the deep and the cultural setting of the series.

Where was the main underwater set constructed?

The primary tank was built at CJ ENM’s studio in Seoul, measuring roughly 15 meters in length and equipped with hidden LED panels to simulate shifting light patterns found beneath the surface.

Did any cast members contribute to the BTS footage?

Yes. Both Jun Ji‑hyun and Lee Min‑ho participated in a special “cast commentary” segment, offering insights on their character arcs and sharing behind‑the‑scenes anecdotes that were later compiled into a DVD extra.

Is there an official playlist for the OST?

The full OST is available on major streaming platforms such as Spotify and Apple Music, curated in the order the songs appear within each episode for an immersive listening experience.