This will become a fairly large section in time, as a lake like Loch Ness is subject to many events and processes which can produce many different surface effects.
A common effect is a calm patch in otherwise rippled
water, and this can give rise to accurate (but misinterpreted) reports
of 10 to 15 metre long "objects" on the surface.
These effects are sometimes described as being "shadows on the water", or "something just beneath the surface". There are hardly any conditions under which these could occur. Shadows need to be cast by something, and that thing has to be between the sun and the surface bearing the shadow.
Large dark objects just beneath the surface are very rarely visible except from very short ranges, as any small-boat sailor will confirm.
© 2001 Dick Raynor.
Another isolated patch of calm water reflects the dark hill side above Temple Pier
Mirage effect in mid-loch, July 1st 2000 © 2001 Dick Raynor.
Raining at Invermoriston © 2001 Dick Raynor.