When are people going to stop demanding proof for things that have been proven over and over again. Instead of trying to prove they exist, study them.
In my family alone there have been three seperate big foot sightings. I have seen one. my brother almost ran into one on his bike. My uncle and his logging crew almost hit one running across the logging road in front of them.
As long as people demand more proof they dont have to accept the reality of supposedly strange creatures. So what if there are big foot or sea serpents. Denying they exist is not going to make them go away. It just makes the person look stupid. .