Pen down some superstitious beliefs related to sailing of ships and sailors.

The pirates believe in ghosts.... particularly the ghosts of those who've gone before them. An example of this would be the reaction to Flint's ghost whispering to George and Tom during the treasure hunt. Another would be Dick Johnson's death after defacing his Bible (cutting paper out of it). Lastly, we can look at the pirates fear of the afterlife..... the fact that they understand their actions will likely close the doors of Heaven upon their arrival. Near the end of the novel, Jim says the following about Silver.....

Of Silver we have heard no more. That formidable seafaring man with one leg has at last gone clean out of my life, but I dare say he met his old negress, and perhaps still lives in comfort with her and Captain Flint. It is to be hoped so, I suppose, for his chances of comfort in anotherworld are very small.