Firth of Forth

The Firth of Forth is the estuary or "firth" of Scotland's River Forth. It flows into the North Sea, between Fife to the north, and West Lothian, the City of Edinburgh and East Lothian to the south. 
Geologically, the Firth of Forth is a fjord, formed by the Forth Glacier in the last glacial period. The river is tidal as far inland as Stirling. 
Traffic is carried across the Firth on the Kincardine Bridge, the Forth Road Bridge and the Forth Rail Bridge. In the 21st century, the Clackmannanshire Bridge has been built close to the Kincardine Bridge and the Queensferry Crossing has been built close to the Forth Road Bridge to handle increased road traffic.
In July 2007, a hovercraft passenger service completed a two week trial between Portobello, Edinburgh and Kirkcaldy, Fife. The trial of the service (marketed as "Forthfast") was hailed as a major operational success, with an average passenger load of 85%. It was predicted to cut congestion for commuters on the Forth road and rail bridges by carrying about 870,000 passengers a year. The service was canceled in 2011.