Xiuying Harbour is a little west of the city centre on Binhai Avenue. Bus number 3 as well as a number of others go here. It is not far from the city centre. I have walked there from the city centre, but it is a long walk.
Ferries depart from here about every 90 minutes to Haian. It takes about 90 minutes. There are also boats to Zhanjiang and Guangzhou. It takes about 20 hours to get to Guangzhou.