It’s important to properly set your expectations before entering Sunless Sea. What it looks like, at first glance, is a game in the vein of Pirates! or Elite – a freeform game set in an open world where you can explore, trade and fight according entirely according to your own whims, clawing your way up from having nothing to owning everything. Sunless Sea has one or two elements in common with this sort of game — especially Pirates! — but it is most definitely not them.
Then there’s the roguelikes, specifically FTL, where you have a concrete goal and meander down an unforgiving, randomly-generated path towards it; where the game is geared towards variety and replayability and the player is intended to experience several dozen unsuccessful attempts before they finally accrue enough experience to crack it open and win. Here the resemblance is stronger, but a direct comparison would still be misleading. Sunless Sea isn’t all that much like FTL either.
In fact if you asked me to find the closest touchstone for the sort of game Sunless Sea is, then I would have to dig very deep into my trove of gaming knowledge as it’s been quite a long time since I played anything like it. Once I came back up, though, I would be holding just one solitary game in my hands, with the following words stencilled across its metaphorical cover:
“King of Dragon Pass.”