David Beattie of the Gillespie House Inn in Nova Scotia recommends Cape Chignecto:
The Bay of Fundy Experience: come and walk on the ocean floor.
Though I live in Canada, I’ve never heard of Chignecto. (It’s a big country.)
map source – brochure PDF – linked from official Provincial Park website
Hmm. The “challenging 51 km long Cape Chignecto Coastal Trail.”
Looks great. We love coastal hikes at besthike.
At Cape Chignecto Provincial Park, towering 180 m (600 ft.) sea cliffs rise from the Bay of Fundy, while the world’s highest tides lap at their base. Best described as a wilderness park, it has … of pristine coastline, deep valleys, sheltered coves, rare plants, and remnant old-growth forests. …
Nova Scotia government Cape Chignecto Provincial Park
There are other good shorter options including the moderately challenging 5km (3.1mi) Fundy Ridge Trail.
And there’s much to do there aside from hiking.
besthike.com 
We haven’t visited our Eastern shores yet, but they are so inviting!
I’ve wondered lately if there are such great hikes on PEI also…
DSD
Actually, I was out in PEI looking for “best hikes”. And came up empty.
There are wonderful beach walks.
But it seemed to me the very best adventure in PEI was the big cycling path across the island. That’s what I did, instead.
“The Confederation Trail, the Prince Edward Island leg of the TransCanada Trail, runs tip-to-tip from Tignish to Elmira and totals 350 km of excellent rolled stone dust surface for cycling and hiking. Frequent villages along the way offer cyclists a convenient selection of accommodations, food and services.”
http://www.gov.pe.ca/visitorsguide/index.php3?number=1009625
I rented from Smooth Cycle:
http://www.smoothcycle.com/
I did just 2 days by bike. But doing the whole thing would be great. VERY FLAT.