From the PDF: This adventure is designed to be used with the game supplement, SEA MAIDENS OF SAN GROPIA. If you do not have that item, don't worry, it is written generically enough that you can insert it into any campaign/system with minor alteration (It is Compatible as-is with 1st Edition, and OSRIC rules). The nature of the adventure requires that characters enter and explore an environment not normal to their experience. In this case, they must spend at least some of their time below the surface of the open sea. This creates extreme stress upon the characters as it requires them to have a means of breathing underwater, as well as dealing with the penalties that occur when combating creatures that dwell in such a place. It is recommended that you provide the characters access to minor magic (i.e., potions of water breathing)that will aide them in their exploration. (An NPC within the village will have at least 6 such items when the characters arrive) Because of the condition just described, it is more favorable for the players to have access to character classes that are beyond the basic core group(cleric, fighter, magic user, thief). By allowing druids and monks, for example, the party might possess skills outside the basic classes that could enhance their chances of success. If you do not wish to allow such classes, then it would be prudent to provide nominal magic items that might help the group in ways that, those mentioned, might have. The beginning of this scenario takes place on land, along the shore of some continent-realm where coastal villages are common. The party of characters will likely arrive by means of roads and horseback. There are no random monster encounters necessary for them to deal with en route unless you wish to create and conduct them yourself.