Caledonian MacBrayne, generally known as CalMac, operates all main services on the Firth of Clyde and to the Inner and Outer Hebrides, sailing to over 20 destinations. Mainland ports which serve the islands in the west include Oban and Kennacraig in Argyll, and Mallaig and Ullapool in the Highlands.
For CalMac ferries, it's recommended to book tickets in advance wherever possible, although you can normally buy foot passenger tickets on the day of travel. If planning on making multiple ferry journeys, you can consider purchasing an Island Hopscotch ticket which combines multiple journeys, or you can leave the car behind and opt for a great value Rail and Sail ticket.