There is no proof of a monster in Lake Ness. Odds are small, as there is little space for a monster to reside within waters that has not been scanned or documented.
Big foot or snow man have pretty much been shot down as either bears or wolves. Any "footage" with such creatures are either inconclusive or easily faked. With the amount of hoaxers out there, especially now in the digital age, its hard to take anything seriously anymore.
I strongly believe that Aliens exists. The amount o possibilities created by time and our universe allows for many forms of life to come into, out of, and stay in existence. Believing that only one solar system in the entire universe, lest even our galaxy, has the correct requirements for breeding life is either ignorant of the odds or perhaps naive at best.
Each of these things are a product of the human imagination and can be disproven with common scientific knoledge. For example, a yeticannot exist because a mammal that size cannot survive in inhospitable places with such low supply of food. Plus, all dna tests done have proven all evidence people have collected to be the dna of a bear. As for aliens, you must understand the sheer scale between us and the closest solar system to realise it's just too far for anything to travel unless these aliens can live for millions of years. Logic people.