Okay, first things first. I can't breathe right now. It's so hard for me to watch dark- under water videos, I didn't even watch the whole footage.
But it is my duty to bring the news so here I am. Sunless Sea's first expansion is darker than the main game and it makes you feel more vulnerable and cold. The Zubmariner DLC is everything I am afraid of and I call it a success. If you are afraid of dark water and jump every time something touch your foot, those huge shadows will be your nightmare.
You can watch the Lights in the Darkness video below.