In "The Seafarers of Catan" the pirate can be used to steal resources from another player by putting him on a hex adjacent to one of their ships. Is it also allowed to place the pirate on the water frame around the edge of the board? In certain circumstances this is the only water next to a player's ships.
Even though Pat provided a formal rule that states that the pirate should be placed only on hexes I want to argue that placing it on the border should be allowed. Simply because the border represents (incomplete) hexes. Also it clearly provides places for boats, settlements and cities there where the normal hexes align with it. The border that my family and I use even has hex shapes drawn on it, most likely suggesting that they are in fact hexes. Please refer to the photo below. We played a Seafarer's scenario including the Cities&Knights extension. Notice the look of the border, and also notice that the pirate is on the border as we have always played it like this.
The rules state (p6):
Like the Robber, you place the pirate in the center of any hex you choose— except that you may only place it on a sea hex.
The frame is not composed of hexes, you cannot place the pirate on it.