Transit visa TWOV China

I fly into and overnight in Shanghai on 28 Dec and the next day 29 Dec I board a cruise ship to Japan. The cruise ship returns on 3 Jan and then I fly out of Shanghai on the 5 Jan at 8.00 pm. Can I use the 72 hour free transit and return to China. I have asked the Chinese visa office and they can't tell me.
What documents are required so I am prepared.