Readymoney beach (signposted further along the Esplanade away from the town centre) is about a 5 minute walk. Good for swimming, rock-pooling and eating the (very good) local ice cream from the van.
There are plenty of walks around Fowey harbour and further afield. Information can be found on the official visitor's site here.
Shorter walks around the harbour include one from Readymoney beach past St. Catherine's Castle on to Gribbin Head (part of the South West Coast Path), and Hall Walk which takes you around the harbour, across via Bodinnick Ferry to Polruan.
Ferries to Polruan run from White House slip in the summer and from the Town Quay all year round.
There is more information at Love Fowey and at Enjoy! the Fowey Gift Shop next to the Church.
Cannis is named after the Cannis rock (and Tim's old house at Fowey secondary school). It is also the name of the tug you may see towing ships in and out of the harbour.
A short history of the house can be found here:
Fore Street, Fowey