I'm pretty sure those stupid things will survive a nuclear bomb. Is mowing an option at all in hopes that if you keep hurting them over and over they will dissipate and the grass might help choke them out?
When it comes to spraying in and around water, that's when it gets tricky. Look up the label for this, Rodeo® Herbicide. It has sandbur in the specimen label list. See if its something you can use.