Loch Ness tours from Edinburgh: the loch, the cruise and the real cost

It is a crack in the country.

The Great Glen is a fault line that runs clean across Scotland from Fort William to Inverness, and Loch Ness fills the deepest part of it. That is why the shape is so unusual: twenty-three miles long, barely a mile wide, and steep on both sides. It is less a lake than a flooded trench.

The depth — around 230 metres at the deepest sounding — means it holds more fresh water than all the lakes of England and Wales together, in a body of water you can see across. That volume also means it never freezes, and it keeps the glen a degree or two milder than the hills either side.

The water is very dark. Peat washes down off the surrounding moor and stains it, and visibility below the first few metres is close to nothing. Every sonar survey ever run on the loch has had to contend with that, and it is a large part of why the stories have lasted: it is a big, deep, opaque body of water, and looking at it does not tell you what is in it.

None of which is why people find it beautiful. The reason is the sides — the hills come straight down to the water for the full length, and on a still morning the whole thing goes flat and reflects them.

The modern legend starts in 1933, when a new road was cut along the northern shore and, for the first time, gave drivers a clear view of the water. Sightings began being reported that summer, a photograph followed in 1934, and the story has never gone away.

What is true is that the loch is enormous, extremely deep and effectively opaque, which makes it very hard to prove a negative. Systematic sonar sweeps and, more recently, environmental DNA sampling of the water have found no evidence of anything unusual living in it. The eDNA work did find a great deal of eel.

The guides on these tours mostly play it straight and tell it as a story about the place rather than a claim about biology, which is the right call. Nobody comes to Loch Ness for a zoology lecture, and nobody should be sold one.

The exhibition at Drumnadrochit takes the same line: it walks through each piece of evidence and what happened to it. It is honest, and it is more interesting than a gift shop full of green plush.