Travel from Hong Kong to Foshan

Hi is anyone aware if the visa you get at the border crossing for the Shenzhen special economic zone allows travel as far as Foshan? I am often in hk on business and would like the ability to make a short notice day trip there. I understand there are ferries that depart hk for Foshan too. Is there anywhere to get an entry permit quickly prior to getting the ferry or on arrival at the other end? Thanks