A mysterious aquatic demon with an elegant humanoid form, defined angular features, and a striking deep blue skin tone cuts through the ocean's depths. Its furrowed brow and menacing sharp teeth are captured mid-snarl, revealing an open mouth that suggests both intimidation and intrigue. Surrounding this creature, an immersive underwater landscape unfolds, dappled with shafts of light piercing through the water and casting dynamic shadows, enhanced by the cinematic capabilities of Unreal Engine 4. The scene is alive with the fluid motion of ocean currents, adding to the demon's otherworldly presence.