Hard to tell on the video, but my first impression was Platypus.  But the shadows are too big for that, kinda like the size of a hippo.  Then I saw the hump on the shadows back, like a camel, but it's too short to be one.  Try to get a picture next time.  If I had to guess though, I'd say it was one of the elusive Humpalottapus's or some variant.