Undiscovered Scotland says this about the Canal:
The Crinan Canal starts at Ardrishaig on Loch Fyne, and ends nine miles away at Crinan on the Sound of Jura. It was designed to provide a quick link between the west coast and islands at one end and the Clyde Estuary at the other, and so avoid the long voyage around the south end of the Kintyre Peninsula.
You can read more here.