Based off hypnagogic hallucinations I had as a kid. Blaktunas aren't fish but sneaky human-sized eyeless penguins who can teleport behind your pillow to jumpscare you. They only come out at night and emit deep-sounding "woo" noises as they bend their flexible beaks against their foreheads as they roam about your room. They are called Blaktunas cause their skin texture is similar to that of canned tuna.