Visa to go to Zhuhai from Shenzhen

Hello,

I will spend a few weeks in SZ, thus I will need a visa to enter mainland China.

But I would also like to spend one or two days in Zhuhai (I will take the ferry in the Shekou port ) and then get back to SZ. Do I need a second visa to go to Zhuhai or to go back to SZ ?

Thanks a lot for your help.