Delicious friends, welcome beneath the waves. With the Submariner DLC, Sunless Sea expands its already murky world to the depths of the Unterzee, offering new locations, dangers, and a whole new layer of stories—if you can survive long enough to reach them. Converting your humble vessel into a submersible, however, is no simple matter. It’s a challenging journey of planning, collecting, and braving the hostile sea. This guide walks you through everything you need to know to earn your submarine and start exploring the eerie undersea zones.

The Basics: What Is Submariner?

Sunless Sea: Zubmariner is more than just an expansion—it’s a transformation. Once you’ve earned the right to refit your ship, you gain access to new zones below the sea’s surface, complete with bizarre fauna, new quests, and heightened peril. As expected from the Sunless Sea universe, these new areas are both thrilling and lethal, with extra dangers like oxygen depletion and submerged hazards waiting to test your mettle.

When to Start the Quest

You can attempt to get your submarine early in your playthrough—but should you? The game won’t stop you from diving into the Submariner content as a fresh-faced captain, but it might not be the best idea. Submariner is dangerous, and the costs involved in the refit can be steep. A wiser path is to progress with an established captain who has solid funds, resources, and some map familiarity. If your last captain just perished in the jaws of a megalops and your new one is already half-dead… maybe hold off.

Where to Begin: Port Carnelian

To initiate the submarine questline, head to Port Carnelian, located in the southern region of the map, slightly inward from the western edge. It’s a dangerous journey, as the seas near Port Carnelian host stronger enemies than you’ll typically encounter in early areas. You’ll need to travel smart and fuel up, but ports along the way offer safe harbors to rest and resupply.

Upon arriving at Port Carnelian, you’ll unlock the quest automatically. It’s easy to find and leads to a hidden workshop where the transformation begins.

Experimental Modifications: Your New Obsession

To begin the refit, you must increase your Experimental Modifications stat to 100. There are multiple ways to build this number:

• Turn in Z-Stories in batches of 3
• Donate an Outlandish Artifact, Extraordinary Implication, or Stygian Ivory
• Pay 75 echoes for every 25 points

If you’re struggling to find relics, focus on earning money and using echoes to cover the gap. Keep an eye out for the necessary items during your normal voyages. Each offers a piece of the puzzle.

Personally, you might find the monetary route the most flexible. Deliver port reports to the Admiralty and visit as many ports as fuel allows. Some pay less, others more, but every report nudges you forward. Running tomb-colonists to Venderbight or doing trade runs can help you build a respectable bank quickly.

You can also establish a tight loop: Port Carnelian isn’t far from London’s Wolfstack Docks, so you can ferry reports and supplies back and forth, earning steadily and staying (mostly) safe. The journey may not be fast, but it’s reliable—and staying alive is often worth more than rushing.

Phase Two: Finding Zonar Schematics

Once your Experimental Modifications hit 100, you’ll receive the next task: retrieve Zonar Schematics. These are hidden aboard a derelict vessel near Khan’s Shadow, which lies east of the Salt Lions, themselves east of Fallen London.

Plot your course carefully. This route can be fraught with danger, especially if your ship or stats are lacking. But the reward is key: bring the schematics back to Port Carnelian to finalize your submarine transformation.

A Cautionary Tale: Plan Ahead

On the way back from Khan’s Shadow, the narrator shares a moment of desperation—fire on board, enemies attacking, a sinking sense of failure. The lesson? Don’t get careless just because you’re close to the finish line. Bring fuel. Keep your hull healthy. Maintain a decent crew count.

And double-check your supplies before launching your submarine. One captain made the classic mistake of submerging without enough fuel and immediately found himself trapped below. Don’t be that captain.

Good News for Future Captains

The first time through, earning your submarine is a long and winding journey. But once you complete the quest on one captain, all your future captains can convert their ships into subs without going through the full process again. This legacy mechanic rewards your persistence and helps you ease into subsequent runs.

The Best Advice: Patience

While you can attempt to rush the submarine questline, it’s often better to let it come later. By then, you’ll have better gear, more reliable income, and a stronger sense of the sea. Losing a captain two steps from success because of overconfidence is a tough pill to swallow—and believe us, it happens. A lot.

Take your time. Build your foundation. The Unterzee is patient—it will wait.

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Final Thoughts

The Submariner content adds incredible depth—literally and narratively—to Sunless Sea. But reaching it is no trivial task. Your best tools will always be caution, foresight, and adaptability. Prepare for every step, don’t rush the process, and always check your supplies before diving into the dark.

See you beneath the waves, captain.