Loch Ness has the largest volume of any Scottish loch. It contains more water than all the English and Welsh lakes put together! It's also the coldest - the water temperature averages a chilly 5 degrees Celsius all year round.

The "coldest" Scottish loch is a title often debated between Loch Etchachan in the Cairngorms and Loch Morar due to depth, but Loch Etchachan is the most consistent winner for sheer icy temperatures. Situated at an elevation of approximately 927 meters (3,041 feet), Loch Etchachan is the highest "large" body of water in the UK. Because of its extreme altitude, it remains frozen for many months of the year, and even in mid-summer, its water temperature rarely rises above 4∘C to 6∘C. For lower-altitude lochs, Loch Ness and Loch Lomond maintain a very stable, cold temperature year-round (around 5∘C to 6∘C) because their immense depth prevents the sun from warming the bulk of the water. However, if you are looking for the most "bracing" swim in Scotland, the high-altitude "corrie" lochs like Etchachan are significantly colder than the famous tourist lochs, often retaining ice floes well into late spring or even early summer.