just found this...
"The breather is a loose one-way valve. If the pressure sucks in, it closes the breather. If the heat builds up, it blows out.
Is there a chance debris could block open the breather? Yes. Is it probable? No. The breather is on top of the pumpkin where there is no debris flying from tires or body and blocked by the frame cross members and underbody.
Could a rock jam it open? No. The way the breather is made the gap has a lip that makes the gap so small, the only possible thing to jam it open is debris like mud if you sunk in up to the axles.
Driving through water, the bow wave is created where most of the water is pushed by the front of the car.
If you want cheap insurance, extend the rear breather. It takes 10 minutes.
But through experience, I have found it not necessary. If I were fording deep water on a regular basis, I would extend to be on the safe side but the rear diff is well protected as is."
It should be fine. The water looked deep only because it created a wave in the front due to me going a little fast. Doing the breather mod this week.