What happens if Aabhaca takes the PC's across the lake without incident? Does he come back to take ferry them back and forth across the lake even after the PC's attack the guards?
When i ran this, Aabhaca was not hostile and took the PCs across the lake to the temple. On the way back out, however, the ferryfrog could smell the blood of his kinsmen on the PCs. After taking them about halfway across the lake Aabhaca attempted to flip the boat and attacked them. One of the PCs passed a Sense Motive check and knew Aabhaca was up to something, and was prepared when the moment came. Aabhaca was easily defeated. All in all, the ferryfrog was much more interesting while speaking to the PCs than he was in combat, what with all of his cryptic talk about meditating upon the darkness of Bhal-Hamatugn and seeking the Smoking Eye.
My PC's are in Bhal Hamatugn at the moment. Only 1 PC spoke Undercommon so he was the only one to speak to the ferryman. That PC spoke to him casually but was a bit confused (and bemused) by his random mumblings. They told him why they were headed across the lake (to find Zenith) but didn't attack him so they made it across the lake without incident.
When the PC's head back across the lake I think he'll take them halfway across again without incident before trying to flip them out of the boat. I don't expect he'll provide much of a challenge but it could make things interesting if he does succeed in flipping the boat.
Olaf the Stout