'Power of water' spell quest?

[JorisS]

Hey all,

was nosing through the items I'm carrying, and found that at some point I purchased a scroll of 'power of water'. If I recall correctly, that was in the Freedom islands, in relation to salvaging the 'Moon ghost' or what it was called (the metal ship that sunk or so). In the item description it says 'quest', but I never got the quest?

Anybody who knows where to pick it up? Hate leaving loose ends behind...