GMC Sierra Denali 2009 Owner's Manual page 299

Driving in Water
CAUTION:
{
Driving through rushing water can be dangerous.
Deep water can sweep your vehicle downstream
and you and your passengers could drown. If it is
only shallow water, it can still wash away the
ground from under your tires, and you could lose
traction and roll the vehicle over. Do not drive
through rushing water.
Heavy rain can mean flash flooding, and flood waters
demand extreme caution.
Find out how deep the water is before driving through it.
Do not try it if it is deep enough to cover the wheel
hubs, axles, or exhaust pipe — you probably will not get
through. Deep water can damage the axle and other
vehicle parts.
If the water is not too deep, drive slowly through it. At
faster speeds, water splashes on the ignition system and
the vehicle can stall. Stalling can also occur if you get
the tailpipe under water. If the tailpipe is under
water, you will never be able to start the engine. When
going through water, remember that when the brakes
get wet, it might take longer to stop. See Driving in Rain
and on Wet Roads on page 4-25.
4-23