D&D.Sci April 2021: Voyages of the Gray Swan

You were prepared for gratitude, a commendation from the Admiral, your own department, parades in your name. You were also prepared to hear that your ‘list of helpful suggestions for ensuring supply ships survive random encounters’ was an impudent insult to the collective intellect of High Command, and receive a public execution for your trouble. What you weren’t prepared for was what happened: being allocated a modest stipend, assigned to a vessel, and told that if you’re so clever you should implement your plans personally.

You have 100gp to spend, and your options are as follows:

Coating the underside of the ship in shark repellent would ensure that no journey would feature shark attacks; however, Vaarsuvius’ Law (“every trip between plot-relevant locations will have exactly one random encounter”) means something else would attack instead.40gp
You’ve given up trying to understand what it is about woodwork that makes its practitioners so good at fighting Crabmonsters, but your findings are undeniable: arming the ship’s carpenters would halve the damage done by Crabmonster attacks.20gp
Offering tribute to the Merpeople would ensure they won’t attack the ship, similar to the effect of shark repellent.45gp
There’s enough space in the lower decks to add up to twenty more oars, so when fleeing is the best option, the entire crew can work together to escape. Each extra oar would decrease the damage done by Krakens and Demon Whales by 2%.1gp/​oar
You wouldn’t think these ships could fit more artillery, but clever ergonomics allow you to add up to three more cannons. Your studies suggest each cannon would reduce the damage suffered in Nessie and Pirate attacks by 10%.10gp/​cannon
Arming the Crow’s Nest with state-of-the-art rifles would give lookouts a 70% chance of ensuring a given Harpy attack does no damage.35gp
Giving the deck crew novelty foam swords to wield alongside their standard-issue cutlasses would improve their effectiveness when fighting Water Elementals, reducing the damage these creatures do by 60%.15gp

You’re completely confident in the effectiveness of your ideas, but much less confident that you know which combination would make the best use of your limited budget. To investigate this angle, you’ve procured a record of random encounters encountered by the ships travelling your assigned route; unfortunately, it’s missing some important information for the ships that sank, due to everyone who could fill in those details being dead.

As you board the Gray Swan (why do they give these ships such charmingly unique names when they’re all built and operated identically?), it occurs to you that this might have been intended as an execution after all. The dataset suggests that without any of your clever plans, the survival rate for a journey along your route is a little below 90%, and the Gray Swan is scheduled to make ten trips – five northbound voyages, five southbound – in quick succession. Hopefully this indicates nothing more than your superiors wanting to test your interventions very very thoroughly.

Your top priority is to save your skin. Secondary priorities are minimizing total damage taken and spending as little gold as possible, to impress High Command and return to their good graces.

What will you do?


  • As a passenger, you’ll be kept away from any fights, but the Gray Swan has no lifeboats; keeping the ship from sinking is necessary and sufficient to ensure your survival.

  • Ships are fully repaired every time they make port.

  • Interventions stack such that two 10% reductions are equivalent to one 20% reduction.

  • Interventions apply such that a 10% reduction to an attack that would do 80% damage does 72% damage instead.

  • Each journey takes a month; it is currently Month 5, Year 1406.)

I’ll be posting an interactive letting you test your decision, along with an explanation of how I generated the dataset, sometime next Monday. I’m giving you a week, but the task shouldn’t take more than a few hours; use Excel, R, Python, a priori knowledge, or whatever other tools you think are appropriate. Let me know in the comments if you have any questions about the scenario.

If you want to investigate collaboratively and/​or call your decisions in advance, feel free to do so in the comments; however, please use spoiler tags or rot13 when sharing inferences/​strategies/​decisions, so people intending to fly solo can look for clarifications without being spoiled.