A day in Cherbourg, a day in Le Havre

I would appreciate any suggestions for touring these cities or areas nearby. We will stop for one day in each of these cities 30 and 31 May 2016 on an extended cruise, from about 8 am until 6 or 7 pm. We recently spent 10 days driving in Normandy and visited Rouen, Honfluer, Giverny, Bayeux, the beaches, and MSM among others and really don't want to return again so soon. Eliminating these destinations seems to leave little in the way of alternatives, so far as I can see when I check the cruise line excursions ( for ideas more than tours) or a place like cruisecritic.com. We like walking through towns for architectural, historical and cultural interest, museums, art; but Le Havre, from what I read, might be limited in that regard? Any suggestions would be welcome. Would getting a bus from Le Havre to Deauville or Trouville be feasible? If only to walk along and see the seaside resorts? Thanks.