On August 21, 2017, I joined my Family in Idaho Falls, Idaho for the Total Eclipse 2017. I was just lucky enough to live nearby and have Family with a home in the path of Totality. We saw a YouTube video by the YouTube channel "SmarterEveryDay" where he talks about Eclipse Shadow Snakes. This got us all excited to watch out for this phenomenon. Long story short we lucked out and saw Shadow Snakes. The video is 1 minute long if you watch around the 30-second mark my cell phone was able to capture the shadow snakes. My Grandma was there and having a hard time seeing them. At about the 38-second mark you can really see the shadow snakes and even tell that my Grandmother could see them by her audible excitement. They are shadows that run parallel next to each other.
Enjoy.
Also if you ever have the chance and are debating on going to see Full Totality I highly recommend it. It's worth it.