The LMTV is a highly capable truck designed to move anything anywhere for the military. They're also popular rescue vehicles because of their ability to drive in high water. But, as the NJ National Guard discovered during the Hurricane Irene aftermath, and as shown in this video, there are limits.
What convinced these two National Guard truck crews to drive through water in downtown Manville that was above both their line-of-sight and the height of their intake is something an angry superior officer is probably going to inquire about.
All we know is the rescuers themselves had to be rescued. They also appear to be unable to swim.
(Thanks to everyone for the tip!)