Crush Depth Apparition as a spooky oneshot

22 May, 2025

WW1 U-Boat, 1917 credit:Imperial War Museums

If the excellent Crush Depth Apparition by Amanda Lee Franck hasn't shown up on your TTRPG sonar yet¹ then you need to dive in immediately. It's a spooky and melancholy slice of RPG indie goodness that deserves to be on your zine stand and brought to your table.

I could gush further, but this post is not intended as a review (though if it were, 5 Stars from me). Rather, I'm providing some tips on how to bring this haunting thing to the table if you're time-limited and want to explore its depths before your scheduling oxygen runs out and you and your players have to resurface into your mundane lives.

Credit to BreadWizard and others on the Between Two Cairns Discord for suggesting some of these and allowing me to float some ideas ahead of my session. Also as ever, thanks to my excellent players for being good sports and agreeing to do this haunted submarine module for our Halloween CovNovCon.

Spoilers for Crush Depth Apparition from here on in

Key CDA Oneshot Tips

If you don't have time for the deep dive, here are the key tips to take away if you're looking to run CDA as a oneshot:

• Share the deliciously murky trailer the author made to get your players hyped for the session

• Offer the excellent Crew NPCs as pregen characters for your players²

• Make clear that the sub has to dive a certain number of times to satisfy the British and its mission

• Once the labyrinth appears, give the players the map of this extradimensional space

• Halfway through your oneshot, compromise the Electra - the Bone Shark and/or The Drowned get into the sub

• Use the Bone Shark as a wandering threat in the labyrinth

• Use The Drowned in Room 5 as a puzzle threatening to flood the labyrinth

They're the surface level tips, now here's the deep dive:

CDA Oneshot Tips Deep Dive

Share the trailer

Seriously. It's great

Use the Crew as pregens

Two things make this tip a must in my book, I'm also not sure on a reread whether this wasn't the intention from the author but here I am making it explicit for you if you're unsure like I was on reading CDA.

Excellent and numerous NPCs

One of the best things about CDA is the character development contained in the quotes that introduces each member of the crew. Here's the one for Dr James Colette, the physician:

"When I was a baby, I was mortally afraid of spiders. I would just bawl and bawl if I saw one, and my mum said, Oh James, what will we do with you? There's always spiders in the world. You can't get away from them. And I said, even at sea? And my mum said, Well, no, not there."

There are 8 NPCs here, each with an amazing character encapsulated in a similar quote. But it's possible in the maelstrom of a oneshot that some of these will be missed entirely by your group. This would be a massive shame given the pearls of brilliance here!

Sparse Character Creation Guidance

In addition, you could legitimately criticise this module for leaving character creation very much up to the GM. Pages 12-15 contain some mechanical support and provide a rules chassis to play with that is light and intuitive. What I was looking for when prepping my CDA oneshot was how to give the players the tools they'd need to engage with the tone and realities of life aboard a prototype submarine in 1902. Hooks, motivations, roles, these things aren't provided in the module for players to roll on a table and create a character that would fit in aboard the Electra.

This is particularly challenging when the module has such a strong sense of tone and historical stickiness with its attention to detail. It's tough to see how players could present interesting characters with depth that fit in this salty grey Atlantic voyage without having a special interest in this topic going in³.

What I'd therefore suggest is taking the 8 crewmembers on p.16-17, keep Captain Tyson and Reginald Bacon⁴ back as NPCs, and then present the remaining 6 crewmembers to your players as pregens.

Keep the name, position on the Electra, add in a Looks and what they're carrying. Then assign them a General and Special training skill as per the character sheet guidance on page 12. Once a player has chosen a pregen, give them their quote from the module and let them run with it.

Here's what I came up with minus the quotes (borrowing from the table structure used to generate The Drowned on p.39 of the module):

Holland 1 Class Submarine in the Imperial Japanese Navy (1940), Credit: Wikimedia Commons

Make clear the sub has to dive

As written, it's not a given that the sub will dive and a cautious crew that gets lucky on the weather table could ensure their vessel stays on the surface. This avoids engaging with the fun spooky stuff that occurs when they move below the waves, leaving the best bits of the module undiscovered!

Address this by making clear to the players that part of their mission is to make a number of test dives to demonstrate the vessel's capabilities underwater. 3 feels like a good number of dives, and it's likely that in a oneshot you won't get past the first dive without everything going awry in any case.

As well as framing this to the players at the outset of the session, you could apply in-character pressure via the British Officer and Captain's conversations with the PCs.

In my game, we started in media res just as the Electra was making ready for its second dive. Through a quiet briefing from the captain to the PCs, we established that the first dive went smoothly enough but some of the initial haunting stuff (details starting on p.27) was circulating as rumours among the crew. The Captain wanted the player characters to keep an eye out for anything unusual on this next dive. The PCs were tasked with dealing with any oddities quickly and quietly without alerting the British Officer. Reginald Bacon played well as haughty, nosey, and irritating, making his rounds through the vessel and assuring the crew that he'd be keeping a close eye on proceedings.

Give the players the Labyrinth Map

Once the PCs discover the labyrinth, the module really jumps off the deep end and things start getting real weird, real fast.

In a oneshot, when you're pushed for time, describing the chambers and how they link together could get confusing and time-consuming so in my run I decided to just give the players the map.

You lose something here for sure, it's no longer labyrinthine if you can see the whole thing after all.

However, the map is so gorgeous that in my session the reveal led to some excited table chatter about what was in these murky rooms and how they could successfully navigate its depths.

It also helped signal that things were now getting very weird and we weren't really doing a submarine sim anymore...

Halfway through, compromise the Electra

Over a longer series of sessions, I think there'd be a great way to run this where you are mostly doing turn of the century submarine sailing things with a rising tide of tension and things getting strange.

For a oneshot, we don't have that luxury so I would suggest plunging the players into a more perilous situation at the halfway mark.

Come back from your comfort break and make things distinctly uncomfortable by implementing one or more of these events:

• the Bone Shark gets into the Electra and begins attacking the crew
• the Drowned breach the hull of the Electra and water starts pouring in
• multiple Electra systems break at once: Ballast tanks, Engines, and the Oxygen supply are all good candidates

This will inevitably shift the tone of your game from what might have been creeping horror in the first half to something far more desperate in the second. With a oneshot though, this is a good way to ensure the players get to experience more of the module and hopefully means you can bring things to a satisfying/unsettling conclusion.

Use the Bone Shark as a wandering threat in the labyrinth

The Ossuary is where this horrific creature initially resides and the module suggests it move between the players and their exit as they explore the labyrinth, ready to pounce as they try to get back to the sub.

If you're short on time though, have the macabre megalodon actively hunt the characters through the labyrinth. The telltale clicking noise of bone on bone should be haunting the players throughout their time in the labyrinth and pile the pressure on.

Use The Drowned in Room 5 as a puzzle threatening to flood the labyrinth

The Drowned are an excellent creepy faction to have roaming the labyrinth and add some moving parts to keep things interesting.

In Room 5 Two Canoes of the labyrinth, there is a unique NPC described as a drowned person who cannot speak but keeps vomiting forth black water. They can communicate through writing (with a tragic story to tell) but at a certain point will just keep shouting and filling that room with black water.

Horrifying!

I would suggest that if the characters don't find a way to deal with them this black water flooding should affect adjacent chambers. Perhaps the hatch to room 5 is badly sealed and black water seeps through. This turns up the pressure further and also ensures they can't just ignore this tragic figure.

SOS (Save Our Storm)

The final section of CDA is The Storm. My group didn't make it this far, they went Home through a doorway in the Labyrinth and had a haunting epilogue instead.

But this final section is chilling and the section cover (p.51) is some of the best art in the book. If you can't get to a satisfactory conclusion on the labyrinth then maybe surfacing and being faced by twelve bell divers standing on the surface of the sea would be a fitting end? Show that cover as your final send off before sinking into the brine...