Theories about Nessie Existence

Science can offer no positive explanation for the sightings, other than optical illusions, misinterpretation of natural phenomena. Many such sightings may actually be due to little known weather phenomena such as "mini" waterspouts.

Judging distance, size and motion of an object in the sea is extremely difficult. Objects on land can be compared to nearby trees, fences or buildings. In the water only the waves offer a clue to scale and the size of waves vary enormously depending on weather conditions. 

The movement of the waves can also suggest motion where there is none. Arthur Adams, a ship’s surgeon in the 1860’s, spotted what appeared to be a mysterious creature moving through the water by using lateral undulations of it’s body. His ship’s course was altered to intercept the animal and capture it. When they approached the thing Adam’s wrote: 

"By this time, however, a closer and more critical inspection had taken place, and the supposed sea monster had turned himself into a long, dark root, gnarled and twisted, of a tree, secured to the moorings of a fishing net, with a strong tide passing it rapidly, and thus giving it an apparent life-like movement and serpentine aspect."

 Some sea monster reports may not involve just unusual creatures, but usual conditions. Right before a storm at sea, air of two different temperatures can form layers just above the surface of the sea. Perhaps seven or eight feet above the waves. The different density of the two layers can cause light to bounce forming a mirage. In this case the mirage causes objects to be elongated, vertically, but not horizontally. Seals, whales and dolphins breaking the surface under these conditions will appear as thin, tall, unknown creatures. 

Norse men often spotted these creatures and took their appearance as an omen warning of an impending storm. Because of the strange atmospheric conditions, rather than anything supernatural, this warning was accurate.

To humans, who have limited exploration of the great depths, the underwater world is filled with mysteries and secrets. A sailor who has been at sea for months could be tempted to stretch an episode to make for a more exciting retelling. Exaggeration may even happen unintentionally. Already equipped with active imaginations, people can easily mistake one thing for another, especially when emotions, such as fear or boredom, are added into the mix.