The Sinking City (Steam - Instant delivery)

https://store.steampowered.com/app/750130/The_Sinking_City/

In the 1920s, on the East Coast of the United States, the half-submerged city of Oakmont is gripped by supernatural forces. You're a private investigator, uncovering the truth of what has possessed the city and corrupted the minds of its inhabitants... and yours.