Travel from Shanghai to Shuhai

I want to travel for business to SHUHAI via SHANGHAI does 72 hours free transit is suffices. I leave China from SHUHAI via embarkation onboard the vessel for Melbourne within the required time frame of 72 hours . Since the Chinese national holiday is ahead, there is no time to proceed with the temporary transit visa. Could you please advise? Thank you in advance. Your quick response is greatly appreciated.