We will be boarding a cruise ship from Shekou port and will be arriving into Shenzhen from HK

and boarding on the same day. As an Australian passport holder can we arrive into SZ and get a SZ visa on arrival via train, or ferry to shekou port and then leave same day via Cruise ship? The cruise ship will not return to SZ to disembark. is this doable and is the train or ferry a better option? Would we need a Chinese visa organised beforehand or is a SZ visa on arrival enough?