The daily sailings of the Calmac ferry around Muck, Eigg, Rum and Canna in Scotland’s Inner Hebrides amount to one of the best-value cruises in the northern hemisphere. Andrew Eames goes exploring—for $20.

It isn’t the usual cruise ship crowd. There are walking parties with dogs. Council workers in overalls. Twitchers—bird spotters—with tripods and chunky zoom lenses. A couple of gamekeepers, looking slightly out of place in their heavy waterproofs. And a bus party of tourists from Scotland’s east coast. All getting on the same boat.

No, I say to myself, it isn’t the usual cruise ship crowd, but then nor would you find the port of Mallaig, on Scotland’s west coast, on a map of cruise ship terminals. On one side of the quay are colorful trawlers and scallop dredgers filling their holds with ice, ready to put to sea, while over at the back, I can see the rail terminus of the West Highland Line, where the steam-hauled Jacobite, which has played the part of the Hogwarts Express in the Harry Potter movies, will be arriving.