Coniston Water

Coniston Water is a lake in the Lake District. It is the third largest lake by volume, after Windermere and Ullswater, and the fifth largest by surface area. The lake is 8.7 kilometres (5.4 mi) long, 730 metres (2,400 ft) wide and 56.1 metres (180 ft) deep. The lake drains into the River Crake, which flows into Morecambe Bay via the estuary of the River Leven.
(Wikipedia)

Coniston Water is a picturesque lake in the shadow of the mighty fell, Old Man of Coniston. At 5 miles (8 km) long and 184 feet (56 m) deep, it is the fifth largest of the national park’s lakes. There are paths around the water's edge that explore lots of little beaches – perfect for relaxing in fine weather.

The Cumbria Way follows the western shore of Coniston Water for 4km. This is a beautiful tranquil section of the path with good views across the lake.
You will often see schools of sailing dinghys and of course the Coniston Launch ferry. There are several jetties where the launch will stop with timetables.
It is much more enjoyable to walk though.