Visa on cruiser

I am an Australian passport holder taking a cruise from Hong Kong on Saturday 11th March to Shanghai via Tianjin., arriving Tianjin on Monday 20th and leaving for Shanghai on Wednesday 22nd. The cruise ends in Shanghai on Saturday 25th morning and I would fly home that evening without staying over night there. My questions are :
1. Do I need a Chinese visa for this cruise.
2. If I do, can it be obtained on board or it has to be ready before commencing the cruise.