Hi all, Long time reader of Physics Forums but first time posting. Anyway, I work for a national magazine, and we are running an article on "Shockwaves". For the picture in the article we are using the attached image (or link here http://commons.wikimedia.org/wiki/File:Uss_iowa_bb-61_pr.jpg). However, from my understanding of shockwaves, this isn't one; it's merely a concussion wave resulting from the explosion from the barrel of the gun. I've been doing a lot of research on the image and several places have identified it as a shockwave, but I don't think it is. Could anyone confirm or deny whether it is or not, and if it's not a shockwave, what is the wave being produced on the water? Does it have any relevance to a shockwave? Thanks!