'Majestic waves' deep beneath the surface of Loch Ness
The movement of warm and cold water creates "huge, majestic waves" deep beneath the surface of Loch Ness.
Scientists have been studying the waves, part of a process called thermocline that begins about 20m (65ft) underwater, for years.
However, many of the thousands of visitors to the loch every year may be unaware of them.
Adrian Shine, an expert on Loch Ness, has recorded the waves moving slowly underwater using sonar.
Mr Shine led a project that included recording this movement of water beneath Loch Ness 24 hours day over a period of about a month.
He told BBC Radio Scotland's Brainwaves programme: "We recorded this huge underwater wave moving under the vessel.
"In the course of an hour the thermocline dropped from 18 metres to 60.
"These great, majestic waves, which are part of the slopping or oscillation that develops in Loch Ness, are only moving at about a kilometre per hour."
Prof Mark Inall, a marine physicist at the Scottish Association for Marine Science in Oban, said the loch's prevailing south-west winds influenced the movement of warm and cold water deep in the loch.
When the wind blows, warm water is pushed towards the Inverness end of the loch where it "piles up" and pushes colder water down and back towards Fort Augustus at the other end of the loch.
In calmer conditions, warm water flows the other way, towards Fort Augustus, and the cold water moves towards Inverness
He said this "see-sawing" of water did not happen in a "nice straight line" but "wobbles".
The physicist said: "It manifests itself as a steep step with lots of little waves behind it. Loch Ness was the first place that these waves were observed in a freshwater loch."