Here's the next map in the chase. Once the PCs jump into the moat, they have to swim and avoid being shot by bowman on the wall parapet, though nobody will jump in after them.
The small tower north of the moat is the Sorcerer's tower and arcane missles will soon be launched. Samurai archers on the south rampart, the other side of the moat, will be firing on PCs swimming in the moat. Eventually sorcerers will be appear at the bottom of the tower in closer proximity.
Before the PCs make it to the opposite side, they will notice a half dozen boats in the moat coming from the north each with samurai archers and ashigaru spear men, poling their way towards the PCs position.
The only escape is through the drainage tunnel on the opposite wall to escape into the next map tile...