I'm not an expert, but I think previous posts have covered the main issues quite well.

Your employer's maintenance contractor should be able to tell you if the vehicle has been 'proofed for water crossings.

If you go through the same crossings regularly, get your crew to pound in metal garden stakes (6' garden T-stakes are cheap) to give a visual indication of the water level. Could save you a lot of grief.

My two-cent's worth.