It's no big deal going through the water with BFDR's. The tread doesn't hold much water (a Nitto would hold more, though).
I used to drive around and back into the water, but found My 60fts or consistancy did not change when I just drove through. I scrub my front tires a little to keep them from tracking water, though....
Turn the tires over once slowly in the water to wet the tread, pull onto the dry and do your burnout.
The water makes the tires spin easier. The easier they spin the less power you need to spin them, the easier on the driveline you will be. Investing in a linelock is a good idea. It will help save the rear brakes and make the burnout that much easier on the driveline.
Do a burnout to clean the tires. Huge burnout are not required if the tires are kept clean. If balls of rubber form on the tires, the burnout was too long. After the first burnout, do not drive through or park in dirt, crushed rock, gravel or grass until you pack up to head home for the night. Of the bad 4, grass is the least evil, but it grows in dirt, which is one of the most evil....
Drag radials work best at tracks that are swept and prepped. Dusty gravelramas on "pickup truck night" and drag radials don't mix.