The Highland Boundary Fault crosses the Firth. The Firth also played a vital military role during World War II. The Firth is sometimes called the Clyde Waters or Clyde Sea, and is customarily considered to be part of the Irish Sea.
The Firth encompasses many islands and peninsulas. Twelve ferry routes connect them to each other and the mainland. The majority of the ferry services are run by Caledonian MacBrayne and one by Western Ferries, and many of the routes are lifeline services for communities living in remote areas. The Firth has no fixed link transport infrastructure connections (bridge or tunnel), linking the shores or islands. The lowest fixed crossing over the Clyde is the Erskine Bridge, opened on 2 July 1971.
With the advent of tourism in Victorian times, the Firth became popular with Glaswegians and residents of neighbouring towns and counties who travelled “doon the watter” (the Firth) on Clyde steamers to holiday in the picturesque seaside towns and villages that line the Firth, with the more wealthy building substantial holiday homes along its coasts. Many towns, such as Gourock, Largs, Ayr, Dunoon, Rothesay, flourished during this period and became fully fledged resorts with well-appointed hotels and attractions. Golf courses, including major championship courses, proliferated.
Today, tourism, sport and recreation, and heritage history continue to attract visitors from across the world. The steam-powered PS Waverley—in addition to its regular service—still makes cruising trips to the coastal towns that have been popular tourist destinations since the 19th century. The Firth is ringed by many castles and buildings of historical importance that are open to the public, including Inveraray Castle, Brodick Castle, the opulent Mount Stuart House on the Isle of Bute, and Culzean Castle, which is the most visited attraction owned by the National Trust for Scotland. Ocean liners frequently call at Greenock, and Glasgow International Airport and Glasgow Prestwick Airport are nearby. There is frequent rail service to and from the Clyde coast, including links to Oban and Fort William, with city terminals in Glasgow and Edinburgh. There is also daily ferry service between the area and Belfast.
