Ferries offer a fun, cost-effective twist on European vacations. Get inspired:

Heading between Britain and Ireland? Cheap train-plus-ferry combination tickets can be purchased at any British or Irish station offering the service. London-Dublin ferry tickets start at £27 (about $53) each way for both train and ferry, via Holyhead in Wales. (You can even buy the tickets at the station on your day of departure.) For comparison's sake, let's say you flew instead between Britain and Ireland. Putting aside the plane ticket cost, the commuter train from central London to the airport would cost around £13 (about $25) on its own, making the train+ferry fare a relative bargain. See www.seat61.com/Ireland.htm.

Going from London to Amsterdam? London to Amsterdam overnight (saving a hotel bill!) costs £59 one-way (about $116) including a private cabin with shower/toilet on the Harwich-Hook of Holland Ferry. You leave central London 8 p.m., arrive in Amsterdam just after 10 a.m. next morning. See www.dutchflyer.co.uk or www.seat61.com/Netherlands.htm.

Exploring the Mediterranean? How about a cruise ferry from Italy to Greece? Several ferry companies make this run, but the best operator on the shortest crossing is generally superfast.com from Bari to Patras (just 3-4 hours train ride from Athens by a scenic, narrow gauge train). Or you can cruise direct from Venice: www.minoan.gr and www.anek.gr both sail this route. If you fancy staying on a Greek island, but aren't sure which ferry goes there, start with the Greek ferry website, www.ferries.gr.

Ferries are also indispensable in the Baltic. Two operators link Stockholm with Helsinki overnight. The evening departure is wonderfully scenic, swiftly passing through some Swedish islands: silja.com and vkingline.com. You’ll also find ships between Helsinki and Tallinn (silja.com, tallink.ee and others) and Stockholm & Tallinn (tallink.ee).

—Mark Smith, blogging from Britain for our Affordable Europe series. See his previous post on saving on trains in Europe.