A firth is a narrow inlet of the sea, often found along the coastlines of countries like Scotland. It is typically formed by the flooding of river valleys and can be characterized by its deep waters and steep sides. Firths are important for navigation and can serve as natural harbors for ships. One of the most famous firths is the Firth of Forth, located in Scotland. This firth is known for its iconic bridges, including the Forth Bridge, and plays a significant role in the local ecosystem and economy. Firths can also support various marine life and recreational activities.