If you're looking for a bit more a free-form, open-world, sandbox-esque horror scenario for your various d100 Cthulhu games, you'll want to check out Raiders of R'lyeh: From the Tideless Sea since that's exactly what it is. An open-world, sandbox adventure with extra help for seafaring during the turn of the 20th century. The book is up on Kickstarter now.
From the campaign:
THE YEAR IS 1900. It is an age of imperial intrigues, daring missions, and creeping dread. Steamships ply the farthest feral seas, and explorers stir the darkest sorceries from forgotten, sunken eons.
YOU ARE A CREW OF ROGUES AND SCOUNDRELS, eking out a living on the tramp steamer S.S. SHANTUNG, hauling contraband and passenger, adventuring port to backwater port, day after weather-beaten day...
And then, on a storm-wracked sea, in a smoke-wreathed tavern, at the blood-stained altar of a savage land, you hear the whisper on the wind, the chant of the beast, the chorus of the mad: CTHULHU…it sleeps…it dreams…it rises...
RAIDERS OF R’LYEH: FROM THE TIDELESS SEA, is our newest expansion for the RAIDERS OF R’LYEH tabletop roleplaying game and other d100 GAMES based on H.P. Lovecraft’s ‘Call of Cthulhu’ and other mythos or pulp stories. Inside this campaign, encompassing 560 pages, mercenary rogues requisition weather-beaten ships, travel strange seas, and challenge an epic and world-spanning, shadowy conspiracy. The expansion is:
- A tribute to the ‘Sargasso Sea’ tales of William Hope Hodgson
- The ultimate horror adventure open world/sandbox
- An epic, world-spanning, earth-shattering conspiracy involving world empires and cosmic forces (inspired by the legendary Masks of Nyarlathotep or Shadows of Yog-Sothoth campaigns for the Call of Cthulhu RPG)
- A massive world sourcebook and collection of toolkits for your own unique Raiders of R’lyeh campaign — or adapted easily for use with other d100 games or settings
The campaign's most of the way to its goal, but only has 5 days left to go.