I'm working on a maritime sandbox adventure for use with Lamentations of the Flame Princess. Sort of.
I'm running it for 1st level characters, with the following changes:
No Clerics, Elves, Dwarves, or Halflings
Instead, Delvers is a class that function like dwarves, and Trackers are a class that function like Halflings. Both are really modified versions of Specialists, so like Specialist kits.
Once I get them written (or find someone else's versions) I'll be set.
We're also using backgrounds and Advantage/Disadvantage from 5e, The Black Hack as much as possible, and spellcasting tables from DCC.
There are physical and mental ACs. Wisdom functions like Sanity, and encountering the undead or extra planar creatures of chaos requires sanity checks -- attack rolls against mental AC, adj by Wisdom, failure suffers a lost point of wisdom. Wisdom score of 0=insanse. Wizards are technically immune to these kinds of encounters, but they are also always borderline insane because of decades spent researching obscure, Eldritch knowledge. Wizards tend to have high Mental ACs and have natural bonuses, plus add intelligence bonus instead of wisdom to their mental AC.
They have learned methods of shielding their minds from alien intrusion.
A wizard's actual wisdom never drops, but they track lost wisdom in the same fashion. When this "imaginary" wisdom reaches 0, they have gone made and/or become possessed by one or more alien minds.
It's a Frankenstein ruleset, we'll see how it plays.
If I can find examples of someone else doing these specific rules changes, I'll apply any lessons they've learned or methods they've used.
The story revolves around a Queens's order to explore a new island chain recently discovered south east of the kingdom. She's already declared the islands as her own, and a ramshackle settlement has been established on the largest of the islands.
The ship the player's are on carries the crew, a team of mercenaries hired to explore the surrounding islands, and settlers willing to join the new settlement and help strengthen the Queen's presence on the islands.
Players choose a background package: Sailing crew, Mercenary, Laborer, Settler, Stoaway, Vistani.
What happens next is completely random; the shipped may be attacked, by pirates or sea monsters. Storms may destroy it or knock it off course; it may find the settlement wiped out; it may end up at a different island, or at an entirely different island chain; it may become lost at sea forever.
All of these possibilities will be determined during the course of play and based on what choices the players make along the way. There is nothing here to railroad their sea-based hex crawl.
This adventure is inspired by watching "In the Heart of the Sea", a movie about the story that inspired Moby Dick, as well as Jacob Hurst's "A Field Guide to Hot Springs Island", Cecil Howe's "Hex Kit", and the 'Maritime Adventures' section of "Lamentations of the Flame Princess".
More to come. Apologies for the bad image; will replace it when I'm home again from Florida (on or after Friday, 9/30).