Ignore these jokesters ( and the instructions on the signpost on the dock ), everyone knows you have to do a mini quest and kill 6 sewer rats on the docks, then find the NPC at the south end of town named 'Timothy' and ask the key word "cross", he will then tell you to kill the banker who dealt him a high interest rate loan, and is now going to lose his fishing boat. You are to ignore his request and 'double cross' him, slaying him quickly... it is a mini quest, so don't worry about getting guard whacked!
Good Luck... the reward for completing the quest is the rights to use his fishing boat ( as you are now owner ) to 'cross' the river!