Once when I was younger, there was this shallow, like 2" deep creek close to my house. I was there one time and I too saw a water mocassin that would not move. I proceeded to find the biggest rock I could find, which was about the size of a basketball. I got on this little bridge over it and threw the rock on it's head. After I did that it started thrashing and writhing around because it's head was stuck. It was funny.