Cruise Ship Visa for China

Just after clarification of another question asked on this board re a cruise - We are on Cruise Ship and enter China via Shanghai on 29 March 2013 - in port 7am to 6pm, then directly on cruise ship to next port arrive 31 March 2013 in Dalian, in port 7am to 2pm, then directly overnight on cruise ship to Tianjin arrive 4am 1 April 2013 - then transfer direct to Beijing Airport for flight 4.50pm to Sydney. So from 7am 29 March until 4.50pm 1 April some 82 hours and having not effectively left China - do we still need a Multi entry visa - can you confirm that this is the situation - thank you