College student-cum-pianist Su-yeon goes into a destructive spiral after he messes up his piano performance. And he's decided getting into bed with strangers is the best way to cope with his anxiety. When he's sleeping with someone, it's like all his troubles just melt away—like he's underwater. During one of his meltdowns, he ends up sleeping with Hae-su, a student-athlete. Except Su-yeon has no memory of the incident. Hae-su re it all however, and when the two end up working together on a group project, he is determined to break down Su-yeon's walls. Hesitant at first, Su-yeon gradually discovers that there's more to life than just being surrounded by shades of blue. Will Hae-su be able to pull Su-yeon from the water he's submerged himself in or will the current be too strong to...resist? (Source: Lezhin) 323i2m

Official Webtoon

Official Translations:
R19: English (Lezhin, Manta), Thai, T.Chinese, Spanish, French, German
R15: English

Notes:
- Lezhin US (R19) and Manta (R15) have different localizations.

- Lezhin US titled the series as 'The Sea's Nocturne', while Manta kept a similar title (Arpeggio on the Surface of the Sea) as the author originally gave it.

- The English, T.Chinese, Spanish, and French versions are uncensored.

- The english version went on a brief hiatus so the creator could replace all the current chapters with the uncensored ones.