A sinister aquatic entity, humanoid in shape, characterized by distinctive angular features and a deep cerulean skin tone, conveys menacing intensity through its furrowed brow and jagged teeth exposed in a gaping maw. Immersed in an ethereal underwater realm, the scene is brought to life with breathtaking cinematic lighting in a 3D environment crafted with Unreal Engine 4, where bioluminescent hues dance across the creature's form, adding an otherworldly glow to its already formidable presence.