Sunless Sea is described as 'Explore the dark and foreboding waters of Fallen London as captain of a steamship. Sunless Sea is an epic, roguelike game of discovery set in the Victorian Gothic universe of Fallen London and played from a real-time, top-down perspective'. There are five games similar to Sunless Sea for a variety of platforms, including Windows, Steam, Mac, Xbox and Linux. The best alternative is Darkwood. It's not free, so if you're looking for a free alternative, you could try Fallen London. Other Sunless Sea like games are Subterrain (Paid), Frozen State (Paid) and The Flame in the Flood (Paid).
Darkwood is a roguelike, survival horror set in ominous, randomly generated woods. FEATURES By day, explore the woods, scavenge for materials and weapons, discover secrets, solve mysteries and talk, trade with or kill the various inhabitants of Darkwood.
Fallen London is a deep and compelling, though ever humorous, journey of interactive fiction set in the dark Victorian-Gothic underworld. It's played in classic, choose-your-own-adventure style where your choices determine how the story plays out.
Travel by foot and by raft down a procedurally-generated river as you scrounge for resources, craft tools, remedy afflictions, evade the vicious wildlife, and most importantly, stay ahead of the coming rains.