The Ghost of Harven Half-Skull

From publisher blurb:

A hundred years ago, Harven Half-Skull was the most feared pirate in the Airdish Sea. No ship from any land was safe from his depredations, and he amassed a huge fortune in plundered loot. Now the ghost of the fearsome buccaneer is once more sailing the Airdish Main, leaving death and destruction in his wake. Can you stop the dead pirate before he adds more poor souls to his undead crew?

This adventure is intended for mid- to high-level characters, and is compatible with most old-school games. It is part of the Greyheim Adventures™ series.