The weird wake phenomenon behind many Loch Ness Monster sightings

The 1958 image above depicts one of the more common kinds of Loch Ness Monster sightings, described by the photographer Peter A MacNab as a "black or dark enormous water creature… cruising on the surface" of the lake. Writing in The Skeptic, Stewart Campbell explains that these kinds of hump sightings and photos may be the result of an unusual wake phenomenon called a Kelvin wake, "peculiar to long and deep narrow lakes used by heavy vessels," such as Loch Ness. From The Skeptic:

The wavefront of a Kelvin wake is complicated, consisting of a series of waves apparently travelling at an angle to the wake itself. This accounts for the series of peaks in the above photo. They themselves can be mistaken for a 'monster'[…]

The phenomenon I refer to is caused by the fact that, in such lakes, particularly if they have steep shores, wakes will be reflected back. Loch Ness is a prime example. A reflected Kelvin wake can then, travelling back from the shore as if they themselves came from a vessel, interfere with the vessel's own wakes, even with the screw wake [caused by the ship's propeller]. The result can be what we might call a 'standing wave': a wave maintaining its appearance, appearing to have its own identity and movement as it is continually fed by various wakes. However this phenomenon needs an almost flat calm water surface, in what some call 'Nessie weather'. Nessie sightings often occur in calm weather, because that is when these wake effects can be seen.

Those strange humps seen in the above image? Likely a Kelvin wake caused by an ice-breaker tug that turned around in Loch Ness's Urquhart Bay.

(via Daily Grail)