Bar Harbor ferry to Canada
1. Re: Bar Harbor to Campobello Island
No ferries from Bar Harbor to anywhere in Canada these days. last one went out of service many years ago.
About two-and-one-half hours driving time, one way, not counting any en route stops.
Whether or not five hours driving to see it in one day is something other folks can't really decide for you. some of us would say, "yes" - others will say 'no". Overnight stay is probably not "necessary", but some folks like to have the experience of staying on-island for its peaceful, extremely laid-back lifestyle.
Most of the folks I know who visit Campobello go for one of two activities: 1) to visit the International Park that includes the summer home of former US President Franklin Delano Roosevelt (you can Google the Park for info on what to see/do there, hours of operation, etc), or 2) to do absolutely nothing except kick back, take a peaceful walk along the shoreline and sip their favorite cold beverage while overlooking the bay.