My rescuee fell into water, how do I carry him back to dry land?

During one of the quests where I have to carry the person I rescued to a certain spot, I put the guy on my horse and rode forth towards the marker on my map. I accidentally rode my horse into water. The guy started swimming towards the bank but once he reached the bank, the wall was too high for him to climb, so he just decided to lie in the water for me to carry him out. The problem is I can't carry people while in the water and trying to retrieve him from up on the bank proved unsuccessful. How do I carry him back to dry land now?