This game is visually lush and rich, but its heart is storytelling.
In this game, you pilot a boat from port to port. You start on the fringe of existence, able to die from a few hits by passing monsters, losing your crew to mob bosses, or running out of fuel or food. Slowly, you crawl your way up to being able to afford more and survive attacks. It calls itself Roguelike in combat and I feel that's accurate.
But most of the gameplay is stories. You discover ports which come in increasingly exotic sets as you get further away from home. At first, you discover things like an island of liars or a mysterious military station accepting coffins and nothing else. As you expand, you can find a terrifying castle of ice or an island of guinea pigs and rats. At the very edges, you reach the truly horrifying or truly cute.
Stories range from diplomatic negotiations to bizarre rituals to painful torture and so on.
The Zubmariner expansion adds a ton of stories but not much new in the way of equipment. The main Zubmariner storyline (Immortality) is excellent, and the new ports are some of my favorites (I enjoyed slowly turning my organs into crystal and injecting myself with solidified regrets).
I put about 76 hours into the game+expansion, and plan on playing again in the future.