Loch Ness is a large, deep, freshwater loch in the Scottish Highlands extending for approximately 37 kilometers southwest of Inverness. Its surface is 16 meters above sea level. Loch Ness is best known for alleged sightings of the cryptozoological Loch Ness Monster, also known affectionately as "Nessie". It is connected at the southern end by the River Oich and a section of the Caledonian Canal to Loch Oich. At the northern end, there is the Bona Narrows which opens out into Loch Dochfour, which feeds the River Ness and a further section of the canal to Inverness. It is one of a series of interconnected, murky bodies of water in Scotland; its water visibility is exceptionally low due to a high peat content in the surrounding soil. Loch Ness is the second largest Scottish loch by surface area at 56 km² after Loch Lomond, but due to its great depth, it is the largest by volume in the British Isles. Its deepest point is 230 m, making it the second deepest loch in Scotland after Loch Morar.