Wether you want to walk, swimm or visit, you are everywere in a few minutes.
Cancale offers a lot of beaches and habors
You can pick up the GR34, a trail along the coast and hike from The Roches Noires to the habor, the pointe du grouin until the Petit-Port beach. You may do the 12 km but it is possible to pick up the trail at many points and walk only bit. You can even walk from Cancale to Saint-Malo, depending on your motivation.